[libcxx][functional][modular] splices <functional> into modular headers

[ldionne]

Some comments, but I like the direction!

libcxx/include/CMakeLists.txt

105–148

I would name those headers without leading underscores. Leading underscores are only useful to avoid conflicting with user-defined macros or user-defined filenames, but we already take our precautions here by using __functional. I think the intent here is to segregate implementation details from the public library API, however I don't think that adding two underscores here is the way to go. If we really wanted to do that, we could use something like detail/ instead (I'm not suggesting we do that at this point in time, only if it becomes helpful to do so).

111–114

I would group all those operations (including the other functional operations like less) into a single header __functional/operations.h or something like that. They are all very similar, do not have major dependencies (beyond unary_function and binary_function), and we don't gain much from splitting them apart IMO.

116–122

I don't think we want to move those to a deprecated subdirectory. Being deprecated is a property that depends on the standard version, and as such, it's not something that is inherent to the utility contained in the file.

[• Quuxplusone]

libcxx/include/CMakeLists.txt

111–114

FWIW, I wasn't going to object to Chris's design here. ;) I personally wouldn't have bothered to split these up, but now that they are split up, I can see certain advantages (as well as disadvantages — but the disadvantages are common to this entire past couple months of refactoring; there's nothing uniquely bad about what's happening with these functional ops).
For example, you'll be able to diff bit_and.h bit_xor.h in order to detect accidental differences between the implementations. With those classes both in the same header, it's much harder to detect accidental differences. (Of course, with those classes in different headers, it's much easier to introduce accidental differences, by forgetting to edit one of the million headers. But we've already committed to that disadvantage.)

116–122

Strongly agreed with @ldionne here. Also, three-level nesting is bad.

libcxx/include/iterator

559 ↗

(On Diff #354573)

I suggest (as a general rule) that removing header dependencies should be done in a separate commit, so that it's easier to revert if we need to.
For example,

#include <iterator>
int main() { typeid(42); }

currently compiles with libc++, but if you remove __functional_base from iterator, then (I think) it stops compiling.

libcxx/include/module.modulemap

455–462

On the one hand, this looks reasonable; on the other hand, I think we need a discussion about three-level nesting. And ideally a discussion about four-level nesting, before someone decides to do it.

[cjdb]

libcxx/include/CMakeLists.txt

105–148

I can get behind a __header/detail approach. __functional/search.h "clashes" with __algorithm/search.h: std::search is in __algorithm, but __functional/search.h is an implementation detail used by __algorithm/search.h, __functional/default_searcher.h, and <regex>.

111–114

Arthur's point is a good maintenance one (that I hadn't considered before).

When designing this, I was going to settle on a smaller set of headers: arithmetic_ops.h, bitwise_ops.h, and comparison_ops.h, logical_ops.h. I decided to split it up even more granularly because I want to minimise name leakage. For example, <numeric> needs std::plus, std::minus, and std::multiplies, but it doesn't need anything else. Similarly, many algorithms only need std::equal_to or std::less, but nothing else. I'd like to minimise the surface area of what is leaked by necessity, which led to having singleton headers.

libcxx/include/iterator

559 ↗

(On Diff #354573)

Hmm, yes, good point (that commit is D104982). I'll track down the names from __functional_base and re-import them here. Thanks for flagging this.

libcxx/include/module.modulemap

455–462

Pinged you on Discord.

[ldionne]

libcxx/include/CMakeLists.txt

105–148

Actually, now that you bring this up, I don't see why __search needs to be in __functional/search.h. I think it should be in __algorithm/search.h directly, and its only caller (default_searcher) should use std::search directly, not std::__search. This can be done as a separate commit, let me know if you'd like me to do it.

111–114

You make a point about maintenance, however putting them in the same header would also lend itself to improvements like defining them automatically with a macro. I also understand @cjdb's point about name leakage, however name leakage isn't really an issue -- those are not macros.

If those had different sets of dependencies, then I wouldn't argue for this at all. However, they are all logically part of the same piece of functionality (providing a named version of various operators), so I think it makes more sense to group them.

[cjdb]

libcxx/include/CMakeLists.txt

105–148

Let's do this in a separate commit. Feel free to do it: just lmk so we don't duplicate work like in <iterator> 🙃

111–114

I also understand @cjdb's point about name leakage, however name leakage isn't really an issue -- those are not macros.

We're talking about different kinds of name leakage. I'm referring to the fact that anyone who includes __functional/operations.h implicitly exports all of the operations, even if they're not necessary. Hyrum's law indicates that <set> (for example) will be used to get function objects, because it can be used. <set> needs to export std::less for a working implementation of std::set, but it doesn't need to export std::greater or std::plus.

If those had different sets of dependencies, then I wouldn't argue for this at all. However, they are all logically part of the same piece of functionality (providing a named version of various operators), so I think it makes more sense to group them.

My argument above can also be made for <numeric>, where this is possibly worse than <set>, because that's where std::accumulate and std::inner_product* live. I wager that folks who understand how a fold operation can be the basis for a great many algorithms will reach for standard function objects more frequently than others. While it would be nice to make their lives easier and export them here, that exposes them to the sharp edge that std::equal_to isn't guaranteed to be provided by <numeric>, exposing their code to non-portability.

*and std::reduce, and std::transform_reduce.

[ldionne]

libcxx/include/CMakeLists.txt

105–148

https://reviews.llvm.org/rGd03aa7d6b66fd741db2d937c18a6c6675037b888

111–114

We're talking about different kinds of name leakage. I'm referring to the fact that anyone who includes __functional/operations.h implicitly exports all of the operations, even if they're not necessary.

I agree that name leakage is bad, and that we can and should take reasonable steps to limit it. I'm personally still paying the price for <memory> once exposing the assert macro through an unfortunate include of <cassert>, which was removed over a year ago.

However, I think we're giving name leakage more importance than it deserves in this instance. Those names are not used *that* often, and people who care that much about name leakage can/should use modules.

I care more about grouping things together coherently when it makes sense and not having to include 19 headers individually than about name leakage, in this specific case.

libcxx/include/__functional/negate.h

3

Please remove the filename here and everywhere else. We shouldn't do that anymore, there's not any benefit AFAICT and we get it wrong when we copy/paste.

[cjdb]

libcxx/include/CMakeLists.txt

105–148

Excellent, thank you!

111–114

We're talking about different kinds of name leakage. I'm referring to the fact that anyone who includes __functional/operations.h implicitly exports all of the operations, even if they're not necessary.

I agree that name leakage is bad, and that we can and should take reasonable steps to limit it. I'm personally still paying the price for <memory> once exposing the assert macro through an unfortunate include of <cassert>, which was removed over a year ago.

However, I think we're giving name leakage more importance than it deserves in this instance. Those names are not used *that* often, and people who care that much about name leakage can/should use modules.

I disagree on both counts. See my point regarding fold operations for the former (and also recognise that std::set<T, std::greater<>> is not an unreasonable thing to spell).

For the latter: enabling modules might not always be possible. GCC doesn't support Clang modules as far as I'm aware, and I'm not exactly sure how many people even know about Clang modules, let alone know why they're useful, or how to use them (properly). Enabling modules requires convincing a project owner that it's worth the buy-in, and that's not always easy/possible. I'm also not sure what effect this will have on people who build everything from source and have upstream dependencies.

I care more about grouping things together coherently when it makes sense and not having to include 19 headers individually than about name leakage, in this specific case.

How about a compromise? We keep the 19 headers, and I add grouped ones for simplicity too. This means we can use individual headers when we only need a small few, and the grouped ones when we need to import pretty much everything.

__functional/arithmetic_ops.h
__functional/bitwise_ops.h
__functional/comparison_ops.h
__functional/logical_ops.h

[• Quuxplusone]

libcxx/include/CMakeLists.txt

111–114

We keep the 19 headers, and I add grouped ones for simplicity too

IMO that would be the worst of all worlds. I'm relatively neutral on "1 header" versus "19 headers" versus "4 headers," but I certainly dislike "19 + 4 = 23 headers."

[cjdb]

• brings <__functional_base> back as a shell to preserve header inclusions in this commit
• removes deprecated directory
• removes underscores from implementation-detail header names

libcxx/include/iterator

559 ↗

(On Diff #354573)

It was easier to bring <__functional_base> back as a zombie. That header can go for real in D104982.

libcxx/include/module.modulemap

455–462

Ping again.

[ldionne]

libcxx/include/__functional/binary_negate.h

10

Those include guards are now wrong!

[cjdb]

* replaces specialisations with _If
* adds tests
* moves borrowed_subrange_t into __range/subrange.h (ATTN @ldionne)

Pushed wrong worktree.

[cjdb]

moves function objects into a single header

[cjdb]

forgot to add the new header

[ldionne]

Commandeering to fix the few last issues and get a CI build going before Chris is up!

libcxx/include/CMakeLists.txt

132–137

The same reasoning that we discussed applies for these operations - let's group them.

Also, let's try to avoid 3 levels of nesting if we can.

libcxx/include/__functional/bind.h

14–19

Please take the habit of sorting includes.

libcxx/include/__functional_base

16

Oops, those haven't been updated.

[ldionne]

Apply final comments and get a CI build going

[ldionne]

CI passing, shipping this now. Thanks @cjdb for doing this work despite our differing views on how to split the functional operations.

libcxx/include/CMakeLists.txt

set(files
   __bits
   __bsd_locale_defaults.h
   __bsd_locale_fallbacks.h
   __config
   __debug
   __errc
   __format/format_error.h
   __format/format_parse_context.h
-  __function_like.h
-  __functional_03
-  __functional_base
-  __functional_base_03
+  __functional/binary_function.h
+  __functional/binary_negate.h
+  __functional/bind_front.h
+  __functional/bind.h
+  __functional/binder1st.h
+  __functional/binder2nd.h
+  __functional/bit_and.h
+  __functional/bit_not.h
+  __functional/bit_or.h
+  __functional/bit_xor.h
+  __functional/default_searcher.h
+  __functional/divides.h
+  __functional/equal_to.h
+  __functional/function.h
+  __functional/greater_equal.h
+  __functional/greater.h
   __functional/hash.h
+  __functional/identity.h
+  __functional/invoke.h
+  __functional/is_transparent.h
+  __functional/less_equal.h
+  __functional/less.h
+  __functional/logical_and.h
+  __functional/logical_not.h
+  __functional/logical_or.h
+  __functional/mem_fn.h
+  __functional/mem_fun_ref.h
+  __functional/minus.h
+  __functional/modulus.h
+  __functional/multiplies.h
+  __functional/negate.h
+  __functional/not_equal_to.h
+  __functional/not_fn.h
+  __functional/perfect_forward.h
+  __functional/plus.h
+  __functional/pointer_to_binary_function.h
+  __functional/pointer_to_unary_function.h
+  __functional/ranges/equal_to.h
+  __functional/ranges/greater_equal.h
+  __functional/ranges/greater.h
+  __functional/ranges/less_equal.h
+  __functional/ranges/less.h
+  __functional/ranges/not_equal_to.h
+  __functional/reference_wrapper.h
   __functional/unary_function.h
+  __functional/unary_negate.h
   __functional/unwrap_ref.h
+  __functional/weak_result_type.h
+  __functional_base
+  __function_like.h
   __hash_table
   __iterator/advance.h
   __iterator/back_insert_iterator.h
   __iterator/concepts.h
   __iterator/default_sentinel.h
   __iterator/front_insert_iterator.h
   __iterator/incrementable_traits.h
   __iterator/insert_iterator.h
set(files
   __iterator/readable_traits.h
   __iterator/reverse_iterator.h
   __iterator/wrap_iter.h
   __libcpp_version
   __locale
   __memory/addressof.h
   __memory/allocation_guard.h
   __memory/allocator.h
+  __memory/allocator_arg_t.h
   __memory/allocator_traits.h
   __memory/auto_ptr.h
   __memory/compressed_pair.h
   __memory/construct_at.h
   __memory/pointer_safety.h
   __memory/pointer_traits.h
   __memory/raw_storage_iterator.h
   __memory/shared_ptr.h
   __memory/temporary_buffer.h
   __memory/uninitialized_algorithms.h
   __memory/unique_ptr.h
+  __memory/uses_allocator.h
   __mutex_base
   __node_handle
   __nullptr
   __random/uniform_int_distribution.h
   __ranges/access.h
   __ranges/all.h
   __ranges/concepts.h
   __ranges/data.h

libcxx/include/__functional/binary_function.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BINARY_FUNCTION_H
+#define _LIBCPP___FUNCTIONAL_BINARY_FUNCTION_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Arg1, class _Arg2, class _Result>
+struct _LIBCPP_TEMPLATE_VIS binary_function
+{
+    typedef _Arg1   first_argument_type;
+    typedef _Arg2   second_argument_type;
+    typedef _Result result_type;
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BINARY_FUNCTION_H

libcxx/include/__functional/binary_negate.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_BINARY_NEGATE_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_BINARY_NEGATE_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS)
+
+template <class _Predicate>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 binary_negate
+    : public binary_function<typename _Predicate::first_argument_type,
+                             typename _Predicate::second_argument_type,
+                             bool>
+{
+    _Predicate __pred_;
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit _LIBCPP_CONSTEXPR_AFTER_CXX11
+    binary_negate(const _Predicate& __pred) : __pred_(__pred) {}
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const typename _Predicate::first_argument_type& __x,
+                    const typename _Predicate::second_argument_type& __y) const
+        {return !__pred_(__x, __y);}
+};
+
+template <class _Predicate>
+_LIBCPP_DEPRECATED_IN_CXX17 inline _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+binary_negate<_Predicate>
+not2(const _Predicate& __pred) {return binary_negate<_Predicate>(__pred);}
+
+#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_BINARY_NEGATE_H

libcxx/include/__functional/bind.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BIND_H
+#define _LIBCPP___FUNCTIONAL_BIND_H
+
+#include <__config>
+#include <__functional/weak_result_type.h>
+#include <__functional/invoke.h>
+#include <cstddef>
+#include <tuple>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template<class _Tp> struct __is_bind_expression : public false_type {};
+template<class _Tp> struct _LIBCPP_TEMPLATE_VIS is_bind_expression
+    : public __is_bind_expression<typename remove_cv<_Tp>::type> {};
+
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t is_bind_expression_v = is_bind_expression<_Tp>::value;
+#endif
+
+template<class _Tp> struct __is_placeholder : public integral_constant<int, 0> {};
+template<class _Tp> struct _LIBCPP_TEMPLATE_VIS is_placeholder
+    : public __is_placeholder<typename remove_cv<_Tp>::type> {};
+
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t is_placeholder_v = is_placeholder<_Tp>::value;
+#endif
+
+namespace placeholders
+{
+
+template <int _Np> struct __ph {};
+
+#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
+_LIBCPP_FUNC_VIS extern const __ph<1>   _1;
+_LIBCPP_FUNC_VIS extern const __ph<2>   _2;
+_LIBCPP_FUNC_VIS extern const __ph<3>   _3;
+_LIBCPP_FUNC_VIS extern const __ph<4>   _4;
+_LIBCPP_FUNC_VIS extern const __ph<5>   _5;
+_LIBCPP_FUNC_VIS extern const __ph<6>   _6;
+_LIBCPP_FUNC_VIS extern const __ph<7>   _7;
+_LIBCPP_FUNC_VIS extern const __ph<8>   _8;
+_LIBCPP_FUNC_VIS extern const __ph<9>   _9;
+_LIBCPP_FUNC_VIS extern const __ph<10> _10;
+#else
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<1>   _1{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<2>   _2{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<3>   _3{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<4>   _4{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<5>   _5{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<6>   _6{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<7>   _7{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<8>   _8{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<9>   _9{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<10> _10{};
+#endif // defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
+
+}  // placeholders
+
+template<int _Np>
+struct __is_placeholder<placeholders::__ph<_Np> >
+    : public integral_constant<int, _Np> {};
+
+
+#ifndef _LIBCPP_CXX03_LANG
+
+template <class _Tp, class _Uj>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp&
+__mu(reference_wrapper<_Tp> __t, _Uj&)
+{
+    return __t.get();
+}
+
+template <class _Ti, class ..._Uj, size_t ..._Indx>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __invoke_of<_Ti&, _Uj...>::type
+__mu_expand(_Ti& __ti, tuple<_Uj...>& __uj, __tuple_indices<_Indx...>)
+{
+    return __ti(_VSTD::forward<_Uj>(_VSTD::get<_Indx>(__uj))...);
+}
+
+template <class _Ti, class ..._Uj>
+inline _LIBCPP_INLINE_VISIBILITY
+typename _EnableIf
+<
+    is_bind_expression<_Ti>::value,
+    __invoke_of<_Ti&, _Uj...>
+>::type
+__mu(_Ti& __ti, tuple<_Uj...>& __uj)
+{
+    typedef typename __make_tuple_indices<sizeof...(_Uj)>::type __indices;
+    return _VSTD::__mu_expand(__ti, __uj, __indices());
+}
+
+template <bool IsPh, class _Ti, class _Uj>
+struct __mu_return2 {};
+
+template <class _Ti, class _Uj>
+struct __mu_return2<true, _Ti, _Uj>
+{
+    typedef typename tuple_element<is_placeholder<_Ti>::value - 1, _Uj>::type type;
+};
+
+template <class _Ti, class _Uj>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if
+<
+    0 < is_placeholder<_Ti>::value,
+    typename __mu_return2<0 < is_placeholder<_Ti>::value, _Ti, _Uj>::type
+>::type
+__mu(_Ti&, _Uj& __uj)
+{
+    const size_t _Indx = is_placeholder<_Ti>::value - 1;
+    return _VSTD::forward<typename tuple_element<_Indx, _Uj>::type>(_VSTD::get<_Indx>(__uj));
+}
+
+template <class _Ti, class _Uj>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if
+<
+    !is_bind_expression<_Ti>::value &&
+    is_placeholder<_Ti>::value == 0 &&
+    !__is_reference_wrapper<_Ti>::value,
+    _Ti&
+>::type
+__mu(_Ti& __ti, _Uj&)
+{
+    return __ti;
+}
+
+template <class _Ti, bool IsReferenceWrapper, bool IsBindEx, bool IsPh,
+          class _TupleUj>
+struct __mu_return_impl;
+
+template <bool _Invokable, class _Ti, class ..._Uj>
+struct __mu_return_invokable  // false
+{
+    typedef __nat type;
+};
+
+template <class _Ti, class ..._Uj>
+struct __mu_return_invokable<true, _Ti, _Uj...>
+{
+    typedef typename __invoke_of<_Ti&, _Uj...>::type type;
+};
+
+template <class _Ti, class ..._Uj>
+struct __mu_return_impl<_Ti, false, true, false, tuple<_Uj...> >
+    : public __mu_return_invokable<__invokable<_Ti&, _Uj...>::value, _Ti, _Uj...>
+{
+};
+
+template <class _Ti, class _TupleUj>
+struct __mu_return_impl<_Ti, false, false, true, _TupleUj>
+{
+    typedef typename tuple_element<is_placeholder<_Ti>::value - 1,
+                                   _TupleUj>::type&& type;
+};
+
+template <class _Ti, class _TupleUj>
+struct __mu_return_impl<_Ti, true, false, false, _TupleUj>
+{
+    typedef typename _Ti::type& type;
+};
+
+template <class _Ti, class _TupleUj>
+struct __mu_return_impl<_Ti, false, false, false, _TupleUj>
+{
+    typedef _Ti& type;
+};
+
+template <class _Ti, class _TupleUj>
+struct __mu_return
+    : public __mu_return_impl<_Ti,
+                              __is_reference_wrapper<_Ti>::value,
+                              is_bind_expression<_Ti>::value,
+                              0 < is_placeholder<_Ti>::value &&
+                              is_placeholder<_Ti>::value <= tuple_size<_TupleUj>::value,
+                              _TupleUj>
+{
+};
+
+template <class _Fp, class _BoundArgs, class _TupleUj>
+struct __is_valid_bind_return
+{
+    static const bool value = false;
+};
+
+template <class _Fp, class ..._BoundArgs, class _TupleUj>
+struct __is_valid_bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj>
+{
+    static const bool value = __invokable<_Fp,
+                    typename __mu_return<_BoundArgs, _TupleUj>::type...>::value;
+};
+
+template <class _Fp, class ..._BoundArgs, class _TupleUj>
+struct __is_valid_bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj>
+{
+    static const bool value = __invokable<_Fp,
+                    typename __mu_return<const _BoundArgs, _TupleUj>::type...>::value;
+};
+
+template <class _Fp, class _BoundArgs, class _TupleUj,
+          bool = __is_valid_bind_return<_Fp, _BoundArgs, _TupleUj>::value>
+struct __bind_return;
+
+template <class _Fp, class ..._BoundArgs, class _TupleUj>
+struct __bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj, true>
+{
+    typedef typename __invoke_of
+    <
+        _Fp&,
+        typename __mu_return
+        <
+            _BoundArgs,
+            _TupleUj
+        >::type...
+    >::type type;
+};
+
+template <class _Fp, class ..._BoundArgs, class _TupleUj>
+struct __bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj, true>
+{
+    typedef typename __invoke_of
+    <
+        _Fp&,
+        typename __mu_return
+        <
+            const _BoundArgs,
+            _TupleUj
+        >::type...
+    >::type type;
+};
+
+template <class _Fp, class _BoundArgs, size_t ..._Indx, class _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __bind_return<_Fp, _BoundArgs, _Args>::type
+__apply_functor(_Fp& __f, _BoundArgs& __bound_args, __tuple_indices<_Indx...>,
+                _Args&& __args)
+{
+    return _VSTD::__invoke(__f, _VSTD::__mu(_VSTD::get<_Indx>(__bound_args), __args)...);
+}
+
+template<class _Fp, class ..._BoundArgs>
+class __bind
+#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : public __weak_result_type<typename decay<_Fp>::type>
+#endif
+{
+protected:
+    typedef typename decay<_Fp>::type _Fd;
+    typedef tuple<typename decay<_BoundArgs>::type...> _Td;
+private:
+    _Fd __f_;
+    _Td __bound_args_;
+
+    typedef typename __make_tuple_indices<sizeof...(_BoundArgs)>::type __indices;
+public:
+    template <class _Gp, class ..._BA,
+              class = typename enable_if
+                               <
+                                  is_constructible<_Fd, _Gp>::value &&
+                                  !is_same<typename remove_reference<_Gp>::type,
+                                           __bind>::value
+                               >::type>
+      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+      explicit __bind(_Gp&& __f, _BA&& ...__bound_args)
+        : __f_(_VSTD::forward<_Gp>(__f)),
+          __bound_args_(_VSTD::forward<_BA>(__bound_args)...) {}
+
+    template <class ..._Args>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+        typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type
+        operator()(_Args&& ...__args)
+        {
+            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
+                                  tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
+        }
+
+    template <class ..._Args>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+        typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type
+        operator()(_Args&& ...__args) const
+        {
+            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
+                                   tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
+        }
+};
+
+template<class _Fp, class ..._BoundArgs>
+struct __is_bind_expression<__bind<_Fp, _BoundArgs...> > : public true_type {};
+
+template<class _Rp, class _Fp, class ..._BoundArgs>
+class __bind_r
+    : public __bind<_Fp, _BoundArgs...>
+{
+    typedef __bind<_Fp, _BoundArgs...> base;
+    typedef typename base::_Fd _Fd;
+    typedef typename base::_Td _Td;
+public:
+    typedef _Rp result_type;
+
+
+    template <class _Gp, class ..._BA,
+              class = typename enable_if
+                               <
+                                  is_constructible<_Fd, _Gp>::value &&
+                                  !is_same<typename remove_reference<_Gp>::type,
+                                           __bind_r>::value
+                               >::type>
+      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+      explicit __bind_r(_Gp&& __f, _BA&& ...__bound_args)
+        : base(_VSTD::forward<_Gp>(__f),
+               _VSTD::forward<_BA>(__bound_args)...) {}
+
+    template <class ..._Args>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+        typename enable_if
+        <
+            is_convertible<typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type,
+                           result_type>::value || is_void<_Rp>::value,
+            result_type
+        >::type
+        operator()(_Args&& ...__args)
+        {
+            typedef __invoke_void_return_wrapper<_Rp> _Invoker;
+            return _Invoker::__call(static_cast<base&>(*this), _VSTD::forward<_Args>(__args)...);
+        }
+
+    template <class ..._Args>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+        typename enable_if
+        <
+            is_convertible<typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type,
+                           result_type>::value || is_void<_Rp>::value,
+            result_type
+        >::type
+        operator()(_Args&& ...__args) const
+        {
+            typedef __invoke_void_return_wrapper<_Rp> _Invoker;
+            return _Invoker::__call(static_cast<base const&>(*this), _VSTD::forward<_Args>(__args)...);
+        }
+};
+
+template<class _Rp, class _Fp, class ..._BoundArgs>
+struct __is_bind_expression<__bind_r<_Rp, _Fp, _BoundArgs...> > : public true_type {};
+
+template<class _Fp, class ..._BoundArgs>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+__bind<_Fp, _BoundArgs...>
+bind(_Fp&& __f, _BoundArgs&&... __bound_args)
+{
+    typedef __bind<_Fp, _BoundArgs...> type;
+    return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
+}
+
+template<class _Rp, class _Fp, class ..._BoundArgs>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+__bind_r<_Rp, _Fp, _BoundArgs...>
+bind(_Fp&& __f, _BoundArgs&&... __bound_args)
+{
+    typedef __bind_r<_Rp, _Fp, _BoundArgs...> type;
+    return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
+}
+
+#endif // _LIBCPP_CXX03_LANG
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BIND_H

libcxx/include/__functional/bind_front.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BIND_FRONT_H
+#define _LIBCPP___FUNCTIONAL_BIND_FRONT_H
+
+#include <__config>
+#include <__functional/perfect_forward.h>
+#include <__functional/invoke.h>
+#include <type_traits>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17
+
+struct __bind_front_op
+{
+    template<class... _Args>
+    constexpr static auto __call(_Args&&... __args)
+    noexcept(noexcept(_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
+    -> decltype(      _VSTD::invoke(_VSTD::forward<_Args>(__args)...))
+    { return          _VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
+};
+
+template<class _Fn, class... _Args,
+         class = _EnableIf<conjunction<is_constructible<decay_t<_Fn>, _Fn>,
+                                       is_move_constructible<decay_t<_Fn>>,
+                                       is_constructible<decay_t<_Args>, _Args>...,
+                                       is_move_constructible<decay_t<_Args>>...
+                                       >::value>>
+constexpr auto bind_front(_Fn&& __f, _Args&&... __args)
+{
+    return __perfect_forward<__bind_front_op, _Fn, _Args...>(_VSTD::forward<_Fn>(__f),
+                                                             _VSTD::forward<_Args>(__args)...);
+}
+
+#endif // _LIBCPP_STD_VER > 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BIND_FRONT_H

libcxx/include/__functional/binder1st.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_BINDER1ST_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_BINDER1ST_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+template <class __Operation>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 binder1st
+    : public unary_function<typename __Operation::second_argument_type,
+                            typename __Operation::result_type>
+{
+protected:
+    __Operation                               op;
+    typename __Operation::first_argument_type value;
+public:
+    _LIBCPP_INLINE_VISIBILITY binder1st(const __Operation& __x,
+                               const typename __Operation::first_argument_type __y)
+        : op(__x), value(__y) {}
+    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
+        (typename __Operation::second_argument_type& __x) const
+            {return op(value, __x);}
+    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
+        (const typename __Operation::second_argument_type& __x) const
+            {return op(value, __x);}
+};
+
+template <class __Operation, class _Tp>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+binder1st<__Operation>
+bind1st(const __Operation& __op, const _Tp& __x)
+    {return binder1st<__Operation>(__op, __x);}
+
+#endif // _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_BINDER1ST_H

libcxx/include/__functional/binder2nd.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_BINDER2ND_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_BINDER2ND_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+template <class __Operation>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 binder2nd
+    : public unary_function<typename __Operation::first_argument_type,
+                            typename __Operation::result_type>
+{
+protected:
+    __Operation                                op;
+    typename __Operation::second_argument_type value;
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    binder2nd(const __Operation& __x, const typename __Operation::second_argument_type __y)
+        : op(__x), value(__y) {}
+    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
+        (      typename __Operation::first_argument_type& __x) const
+            {return op(__x, value);}
+    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
+        (const typename __Operation::first_argument_type& __x) const
+            {return op(__x, value);}
+};
+
+template <class __Operation, class _Tp>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+binder2nd<__Operation>
+bind2nd(const __Operation& __op, const _Tp& __x)
+    {return binder2nd<__Operation>(__op, __x);}
+
+#endif // _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_BINDER2ND_H

libcxx/include/__functional/bit_and.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BIT_AND_H
+#define _LIBCPP___FUNCTIONAL_BIT_AND_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS bit_and
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x & __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS bit_and<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) & _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) & _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) & _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BIT_AND_H

libcxx/include/__functional/bit_not.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BIT_NOT_H
+#define _LIBCPP___FUNCTIONAL_BIT_NOT_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 11
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+template <class _Tp = void>
+struct _LIBCPP_TEMPLATE_VIS bit_not
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : unary_function<_Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x) const
+        {return ~__x;}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS bit_not<void>
+{
+    template <class _Tp>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_Tp&& __x) const
+    _NOEXCEPT_(noexcept(~_VSTD::forward<_Tp>(__x)))
+    -> decltype        (~_VSTD::forward<_Tp>(__x))
+        { return        ~_VSTD::forward<_Tp>(__x); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BIT_NOT_H

libcxx/include/__functional/bit_or.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BIT_OR_H
+#define _LIBCPP___FUNCTIONAL_BIT_OR_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS bit_or
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x | __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS bit_or<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) | _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) | _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) | _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BIT_OR_H

libcxx/include/__functional/bit_xor.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_BIT_XOR_H
+#define _LIBCPP___FUNCTIONAL_BIT_XOR_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS bit_xor
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x ^ __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS bit_xor<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) ^ _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) ^ _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) ^ _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_BIT_XOR_H

libcxx/include/__functional/default_searcher.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEFAULT_SEARCHER_H
+#define _LIBCPP___FUNCTIONAL_DEFAULT_SEARCHER_H
+
+#include <__config>
+#include <__algorithm/search.h>
+#include <__iterator/iterator_traits.h>
+#include <__functional/equal_to.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+// default searcher
+template<class _ForwardIterator, class _BinaryPredicate = equal_to<>>
+class _LIBCPP_TEMPLATE_VIS default_searcher {
+public:
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    default_searcher(_ForwardIterator __f, _ForwardIterator __l,
+                       _BinaryPredicate __p = _BinaryPredicate())
+        : __first_(__f), __last_(__l), __pred_(__p) {}
+
+    template <typename _ForwardIterator2>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    pair<_ForwardIterator2, _ForwardIterator2>
+    operator () (_ForwardIterator2 __f, _ForwardIterator2 __l) const
+    {
+        return _VSTD::__search(__f, __l, __first_, __last_, __pred_,
+            typename iterator_traits<_ForwardIterator>::iterator_category(),
+            typename iterator_traits<_ForwardIterator2>::iterator_category());
+    }
+
+private:
+    _ForwardIterator __first_;
+    _ForwardIterator __last_;
+    _BinaryPredicate __pred_;
+    };
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEFAULT_SEARCHER_H

libcxx/include/__functional/divides.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DIVIDES_H
+#define _LIBCPP___FUNCTIONAL_DIVIDES_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS divides
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x / __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS divides<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) / _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) / _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) / _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DIVIDES_H

libcxx/include/__functional/equal_to.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_EQUAL_TO_H
+#define _LIBCPP___FUNCTIONAL_EQUAL_TO_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS equal_to
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x == __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS equal_to<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) == _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) == _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) == _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_EQUAL_TO_H

libcxx/include/__functional/function.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_FUNCTIONAL_03
-#define _LIBCPP_FUNCTIONAL_03
+#ifndef _LIBCPP___FUNCTIONAL_FUNCTION_H
+#define _LIBCPP___FUNCTIONAL_FUNCTION_H
 
-// manual variadic expansion for <functional>
+#include <__config>
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/unary_function.h>
+#include <__iterator/iterator_traits.h>
+#include <__memory/allocator_traits.h>
+#include <__memory/compressed_pair.h>
+#include <__memory/shared_ptr.h>
+#include <exception>
+#include <memory> // TODO: replace with <__memory/__builtin_new_allocator.h>
+#include <type_traits>
+#include <utility>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// bad_function_call
+
+class _LIBCPP_EXCEPTION_ABI bad_function_call
+    : public exception
+{
+#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+public:
+    virtual ~bad_function_call() _NOEXCEPT;
+
+    virtual const char* what() const _NOEXCEPT;
+#endif
+};
+
+_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
+void __throw_bad_function_call()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_function_call();
+#else
+    _VSTD::abort();
+#endif
+}
+
+#if defined(_LIBCPP_CXX03_LANG) && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS) && __has_attribute(deprecated)
+#   define _LIBCPP_DEPRECATED_CXX03_FUNCTION \
+        __attribute__((deprecated("Using std::function in C++03 is not supported anymore. Please upgrade to C++11 or later, or use a different type")))
+#else
+#   define _LIBCPP_DEPRECATED_CXX03_FUNCTION /* nothing */
+#endif
+
+template<class _Fp> class _LIBCPP_DEPRECATED_CXX03_FUNCTION _LIBCPP_TEMPLATE_VIS function; // undefined
+
+namespace __function
+{
+
+template<class _Rp>
+struct __maybe_derive_from_unary_function
+{
+};
+
+template<class _Rp, class _A1>
+struct __maybe_derive_from_unary_function<_Rp(_A1)>
+    : public unary_function<_A1, _Rp>
+{
+};
+
+template<class _Rp>
+struct __maybe_derive_from_binary_function
+{
+};
+
+template<class _Rp, class _A1, class _A2>
+struct __maybe_derive_from_binary_function<_Rp(_A1, _A2)>
+    : public binary_function<_A1, _A2, _Rp>
+{
+};
+
+template <class _Fp>
+_LIBCPP_INLINE_VISIBILITY
+bool __not_null(_Fp const&) { return true; }
+
+template <class _Fp>
+_LIBCPP_INLINE_VISIBILITY
+bool __not_null(_Fp* __ptr) { return __ptr; }
+
+template <class _Ret, class _Class>
+_LIBCPP_INLINE_VISIBILITY
+bool __not_null(_Ret _Class::*__ptr) { return __ptr; }
+
+template <class _Fp>
+_LIBCPP_INLINE_VISIBILITY
+bool __not_null(function<_Fp> const& __f) { return !!__f; }
+
+#ifdef _LIBCPP_HAS_EXTENSION_BLOCKS
+template <class _Rp, class ..._Args>
+_LIBCPP_INLINE_VISIBILITY
+bool __not_null(_Rp (^__p)(_Args...)) { return __p; }
+#endif
+
+} // namespace __function
+
+#ifndef _LIBCPP_CXX03_LANG
+
+namespace __function {
+
+// __alloc_func holds a functor and an allocator.
+
+template <class _Fp, class _Ap, class _FB> class __alloc_func;
+template <class _Fp, class _FB>
+class __default_alloc_func;
+
+template <class _Fp, class _Ap, class _Rp, class... _ArgTypes>
+class __alloc_func<_Fp, _Ap, _Rp(_ArgTypes...)>
+{
+    __compressed_pair<_Fp, _Ap> __f_;
+
+  public:
+    typedef _LIBCPP_NODEBUG_TYPE _Fp _Target;
+    typedef _LIBCPP_NODEBUG_TYPE _Ap _Alloc;
+
+    _LIBCPP_INLINE_VISIBILITY
+    const _Target& __target() const { return __f_.first(); }
+
+    // WIN32 APIs may define __allocator, so use __get_allocator instead.
+    _LIBCPP_INLINE_VISIBILITY
+    const _Alloc& __get_allocator() const { return __f_.second(); }
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __alloc_func(_Target&& __f)
+        : __f_(piecewise_construct, _VSTD::forward_as_tuple(_VSTD::move(__f)),
+               _VSTD::forward_as_tuple())
+    {
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __alloc_func(const _Target& __f, const _Alloc& __a)
+        : __f_(piecewise_construct, _VSTD::forward_as_tuple(__f),
+               _VSTD::forward_as_tuple(__a))
+    {
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __alloc_func(const _Target& __f, _Alloc&& __a)
+        : __f_(piecewise_construct, _VSTD::forward_as_tuple(__f),
+               _VSTD::forward_as_tuple(_VSTD::move(__a)))
+    {
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __alloc_func(_Target&& __f, _Alloc&& __a)
+        : __f_(piecewise_construct, _VSTD::forward_as_tuple(_VSTD::move(__f)),
+               _VSTD::forward_as_tuple(_VSTD::move(__a)))
+    {
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    _Rp operator()(_ArgTypes&&... __arg)
+    {
+        typedef __invoke_void_return_wrapper<_Rp> _Invoker;
+        return _Invoker::__call(__f_.first(),
+                                _VSTD::forward<_ArgTypes>(__arg)...);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __alloc_func* __clone() const
+    {
+        typedef allocator_traits<_Alloc> __alloc_traits;
+        typedef
+            typename __rebind_alloc_helper<__alloc_traits, __alloc_func>::type
+                _AA;
+        _AA __a(__f_.second());
+        typedef __allocator_destructor<_AA> _Dp;
+        unique_ptr<__alloc_func, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
+        ::new ((void*)__hold.get()) __alloc_func(__f_.first(), _Alloc(__a));
+        return __hold.release();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void destroy() _NOEXCEPT { __f_.~__compressed_pair<_Target, _Alloc>(); }
+
+    static void __destroy_and_delete(__alloc_func* __f) {
+      typedef allocator_traits<_Alloc> __alloc_traits;
+      typedef typename __rebind_alloc_helper<__alloc_traits, __alloc_func>::type
+          _FunAlloc;
+      _FunAlloc __a(__f->__get_allocator());
+      __f->destroy();
+      __a.deallocate(__f, 1);
+    }
+};
+
+template <class _Fp, class _Rp, class... _ArgTypes>
+class __default_alloc_func<_Fp, _Rp(_ArgTypes...)> {
+  _Fp __f_;
+
+public:
+  typedef _LIBCPP_NODEBUG_TYPE _Fp _Target;
+
+  _LIBCPP_INLINE_VISIBILITY
+  const _Target& __target() const { return __f_; }
+
+  _LIBCPP_INLINE_VISIBILITY
+  explicit __default_alloc_func(_Target&& __f) : __f_(_VSTD::move(__f)) {}
+
+  _LIBCPP_INLINE_VISIBILITY
+  explicit __default_alloc_func(const _Target& __f) : __f_(__f) {}
+
+  _LIBCPP_INLINE_VISIBILITY
+  _Rp operator()(_ArgTypes&&... __arg) {
+    typedef __invoke_void_return_wrapper<_Rp> _Invoker;
+    return _Invoker::__call(__f_, _VSTD::forward<_ArgTypes>(__arg)...);
+  }
+
+  _LIBCPP_INLINE_VISIBILITY
+  __default_alloc_func* __clone() const {
+      __builtin_new_allocator::__holder_t __hold =
+        __builtin_new_allocator::__allocate_type<__default_alloc_func>(1);
+    __default_alloc_func* __res =
+        ::new ((void*)__hold.get()) __default_alloc_func(__f_);
+    (void)__hold.release();
+    return __res;
+  }
+
+  _LIBCPP_INLINE_VISIBILITY
+  void destroy() _NOEXCEPT { __f_.~_Target(); }
+
+  static void __destroy_and_delete(__default_alloc_func* __f) {
+    __f->destroy();
+      __builtin_new_allocator::__deallocate_type<__default_alloc_func>(__f, 1);
+  }
+};
+
+// __base provides an abstract interface for copyable functors.
+
+template<class _Fp> class _LIBCPP_TEMPLATE_VIS __base;
+
+template<class _Rp, class ..._ArgTypes>
+class __base<_Rp(_ArgTypes...)>
+{
+    __base(const __base&);
+    __base& operator=(const __base&);
+public:
+    _LIBCPP_INLINE_VISIBILITY __base() {}
+    _LIBCPP_INLINE_VISIBILITY virtual ~__base() {}
+    virtual __base* __clone() const = 0;
+    virtual void __clone(__base*) const = 0;
+    virtual void destroy() _NOEXCEPT = 0;
+    virtual void destroy_deallocate() _NOEXCEPT = 0;
+    virtual _Rp operator()(_ArgTypes&& ...) = 0;
+#ifndef _LIBCPP_NO_RTTI
+    virtual const void* target(const type_info&) const _NOEXCEPT = 0;
+    virtual const std::type_info& target_type() const _NOEXCEPT = 0;
+#endif // _LIBCPP_NO_RTTI
+};
+
+// __func implements __base for a given functor type.
+
+template<class _FD, class _Alloc, class _FB> class __func;
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+class __func<_Fp, _Alloc, _Rp(_ArgTypes...)>
+    : public  __base<_Rp(_ArgTypes...)>
+{
+    __alloc_func<_Fp, _Alloc, _Rp(_ArgTypes...)> __f_;
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __func(_Fp&& __f)
+        : __f_(_VSTD::move(__f)) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __func(const _Fp& __f, const _Alloc& __a)
+        : __f_(__f, __a) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __func(const _Fp& __f, _Alloc&& __a)
+        : __f_(__f, _VSTD::move(__a)) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __func(_Fp&& __f, _Alloc&& __a)
+        : __f_(_VSTD::move(__f), _VSTD::move(__a)) {}
+
+    virtual __base<_Rp(_ArgTypes...)>* __clone() const;
+    virtual void __clone(__base<_Rp(_ArgTypes...)>*) const;
+    virtual void destroy() _NOEXCEPT;
+    virtual void destroy_deallocate() _NOEXCEPT;
+    virtual _Rp operator()(_ArgTypes&&... __arg);
+#ifndef _LIBCPP_NO_RTTI
+    virtual const void* target(const type_info&) const _NOEXCEPT;
+    virtual const std::type_info& target_type() const _NOEXCEPT;
+#endif // _LIBCPP_NO_RTTI
+};
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+__base<_Rp(_ArgTypes...)>*
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::__clone() const
+{
+    typedef allocator_traits<_Alloc> __alloc_traits;
+    typedef typename __rebind_alloc_helper<__alloc_traits, __func>::type _Ap;
+    _Ap __a(__f_.__get_allocator());
+    typedef __allocator_destructor<_Ap> _Dp;
+    unique_ptr<__func, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
+    ::new ((void*)__hold.get()) __func(__f_.__target(), _Alloc(__a));
+    return __hold.release();
+}
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+void
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::__clone(__base<_Rp(_ArgTypes...)>* __p) const
+{
+    ::new ((void*)__p) __func(__f_.__target(), __f_.__get_allocator());
+}
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+void
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::destroy() _NOEXCEPT
+{
+    __f_.destroy();
+}
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+void
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::destroy_deallocate() _NOEXCEPT
+{
+    typedef allocator_traits<_Alloc> __alloc_traits;
+    typedef typename __rebind_alloc_helper<__alloc_traits, __func>::type _Ap;
+    _Ap __a(__f_.__get_allocator());
+    __f_.destroy();
+    __a.deallocate(this, 1);
+}
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+_Rp
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::operator()(_ArgTypes&& ... __arg)
+{
+    return __f_(_VSTD::forward<_ArgTypes>(__arg)...);
+}
+
+#ifndef _LIBCPP_NO_RTTI
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+const void*
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target(const type_info& __ti) const _NOEXCEPT
+{
+    if (__ti == typeid(_Fp))
+        return &__f_.__target();
+    return nullptr;
+}
+
+template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
+const std::type_info&
+__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target_type() const _NOEXCEPT
+{
+    return typeid(_Fp);
+}
+
+#endif // _LIBCPP_NO_RTTI
+
+// __value_func creates a value-type from a __func.
+
+template <class _Fp> class __value_func;
+
+template <class _Rp, class... _ArgTypes> class __value_func<_Rp(_ArgTypes...)>
+{
+    typename aligned_storage<3 * sizeof(void*)>::type __buf_;
+
+    typedef __base<_Rp(_ArgTypes...)> __func;
+    __func* __f_;
+
+    _LIBCPP_NO_CFI static __func* __as_base(void* p)
+    {
+        return reinterpret_cast<__func*>(p);
+    }
+
+  public:
+    _LIBCPP_INLINE_VISIBILITY
+    __value_func() _NOEXCEPT : __f_(nullptr) {}
+
+    template <class _Fp, class _Alloc>
+    _LIBCPP_INLINE_VISIBILITY __value_func(_Fp&& __f, const _Alloc& __a)
+        : __f_(nullptr)
+    {
+        typedef allocator_traits<_Alloc> __alloc_traits;
+        typedef __function::__func<_Fp, _Alloc, _Rp(_ArgTypes...)> _Fun;
+        typedef typename __rebind_alloc_helper<__alloc_traits, _Fun>::type
+            _FunAlloc;
+
+        if (__function::__not_null(__f))
+        {
+            _FunAlloc __af(__a);
+            if (sizeof(_Fun) <= sizeof(__buf_) &&
+                is_nothrow_copy_constructible<_Fp>::value &&
+                is_nothrow_copy_constructible<_FunAlloc>::value)
+            {
+                __f_ =
+                    ::new ((void*)&__buf_) _Fun(_VSTD::move(__f), _Alloc(__af));
+            }
+            else
+            {
+                typedef __allocator_destructor<_FunAlloc> _Dp;
+                unique_ptr<__func, _Dp> __hold(__af.allocate(1), _Dp(__af, 1));
+                ::new ((void*)__hold.get()) _Fun(_VSTD::move(__f), _Alloc(__a));
+                __f_ = __hold.release();
+            }
+        }
+    }
+
+    template <class _Fp,
+        class = typename enable_if<!is_same<typename decay<_Fp>::type, __value_func>::value>::type>
+    _LIBCPP_INLINE_VISIBILITY explicit __value_func(_Fp&& __f)
+        : __value_func(_VSTD::forward<_Fp>(__f), allocator<_Fp>()) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    __value_func(const __value_func& __f)
+    {
+        if (__f.__f_ == nullptr)
+            __f_ = nullptr;
+        else if ((void*)__f.__f_ == &__f.__buf_)
+        {
+            __f_ = __as_base(&__buf_);
+            __f.__f_->__clone(__f_);
+        }
+        else
+            __f_ = __f.__f_->__clone();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __value_func(__value_func&& __f) _NOEXCEPT
+    {
+        if (__f.__f_ == nullptr)
+            __f_ = nullptr;
+        else if ((void*)__f.__f_ == &__f.__buf_)
+        {
+            __f_ = __as_base(&__buf_);
+            __f.__f_->__clone(__f_);
+        }
+        else
+        {
+            __f_ = __f.__f_;
+            __f.__f_ = nullptr;
+        }
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    ~__value_func()
+    {
+        if ((void*)__f_ == &__buf_)
+            __f_->destroy();
+        else if (__f_)
+            __f_->destroy_deallocate();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __value_func& operator=(__value_func&& __f)
+    {
+        *this = nullptr;
+        if (__f.__f_ == nullptr)
+            __f_ = nullptr;
+        else if ((void*)__f.__f_ == &__f.__buf_)
+        {
+            __f_ = __as_base(&__buf_);
+            __f.__f_->__clone(__f_);
+        }
+        else
+        {
+            __f_ = __f.__f_;
+            __f.__f_ = nullptr;
+        }
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __value_func& operator=(nullptr_t)
+    {
+        __func* __f = __f_;
+        __f_ = nullptr;
+        if ((void*)__f == &__buf_)
+            __f->destroy();
+        else if (__f)
+            __f->destroy_deallocate();
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    _Rp operator()(_ArgTypes&&... __args) const
+    {
+        if (__f_ == nullptr)
+            __throw_bad_function_call();
+        return (*__f_)(_VSTD::forward<_ArgTypes>(__args)...);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void swap(__value_func& __f) _NOEXCEPT
+    {
+        if (&__f == this)
+            return;
+        if ((void*)__f_ == &__buf_ && (void*)__f.__f_ == &__f.__buf_)
+        {
+            typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
+            __func* __t = __as_base(&__tempbuf);
+            __f_->__clone(__t);
+            __f_->destroy();
+            __f_ = nullptr;
+            __f.__f_->__clone(__as_base(&__buf_));
+            __f.__f_->destroy();
+            __f.__f_ = nullptr;
+            __f_ = __as_base(&__buf_);
+            __t->__clone(__as_base(&__f.__buf_));
+            __t->destroy();
+            __f.__f_ = __as_base(&__f.__buf_);
+        }
+        else if ((void*)__f_ == &__buf_)
+        {
+            __f_->__clone(__as_base(&__f.__buf_));
+            __f_->destroy();
+            __f_ = __f.__f_;
+            __f.__f_ = __as_base(&__f.__buf_);
+        }
+        else if ((void*)__f.__f_ == &__f.__buf_)
+        {
+            __f.__f_->__clone(__as_base(&__buf_));
+            __f.__f_->destroy();
+            __f.__f_ = __f_;
+            __f_ = __as_base(&__buf_);
+        }
+        else
+            _VSTD::swap(__f_, __f.__f_);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit operator bool() const _NOEXCEPT { return __f_ != nullptr; }
+
+#ifndef _LIBCPP_NO_RTTI
+    _LIBCPP_INLINE_VISIBILITY
+    const std::type_info& target_type() const _NOEXCEPT
+    {
+        if (__f_ == nullptr)
+            return typeid(void);
+        return __f_->target_type();
+    }
+
+    template <typename _Tp>
+    _LIBCPP_INLINE_VISIBILITY const _Tp* target() const _NOEXCEPT
+    {
+        if (__f_ == nullptr)
+            return nullptr;
+        return (const _Tp*)__f_->target(typeid(_Tp));
+    }
+#endif // _LIBCPP_NO_RTTI
+};
+
+// Storage for a functor object, to be used with __policy to manage copy and
+// destruction.
+union __policy_storage
+{
+    mutable char __small[sizeof(void*) * 2];
+    void* __large;
+};
+
+// True if _Fun can safely be held in __policy_storage.__small.
+template <typename _Fun>
+struct __use_small_storage
+    : public integral_constant<
+          bool, sizeof(_Fun) <= sizeof(__policy_storage) &&
+                    _LIBCPP_ALIGNOF(_Fun) <= _LIBCPP_ALIGNOF(__policy_storage) &&
+                    is_trivially_copy_constructible<_Fun>::value &&
+                    is_trivially_destructible<_Fun>::value> {};
+
+// Policy contains information about how to copy, destroy, and move the
+// underlying functor. You can think of it as a vtable of sorts.
+struct __policy
+{
+    // Used to copy or destroy __large values. null for trivial objects.
+    void* (*const __clone)(const void*);
+    void (*const __destroy)(void*);
+
+    // True if this is the null policy (no value).
+    const bool __is_null;
+
+    // The target type. May be null if RTTI is disabled.
+    const std::type_info* const __type_info;
+
+    // Returns a pointer to a static policy object suitable for the functor
+    // type.
+    template <typename _Fun>
+    _LIBCPP_INLINE_VISIBILITY static const __policy* __create()
+    {
+        return __choose_policy<_Fun>(__use_small_storage<_Fun>());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static const __policy* __create_empty()
+    {
+        static const _LIBCPP_CONSTEXPR __policy __policy_ = {nullptr, nullptr,
+                                                             true,
+#ifndef _LIBCPP_NO_RTTI
+                                                             &typeid(void)
+#else
+                                                             nullptr
+#endif
+        };
+        return &__policy_;
+    }
+
+  private:
+    template <typename _Fun> static void* __large_clone(const void* __s)
+    {
+        const _Fun* __f = static_cast<const _Fun*>(__s);
+        return __f->__clone();
+    }
+
+    template <typename _Fun>
+    static void __large_destroy(void* __s) {
+      _Fun::__destroy_and_delete(static_cast<_Fun*>(__s));
+    }
+
+    template <typename _Fun>
+    _LIBCPP_INLINE_VISIBILITY static const __policy*
+    __choose_policy(/* is_small = */ false_type) {
+      static const _LIBCPP_CONSTEXPR __policy __policy_ = {
+          &__large_clone<_Fun>, &__large_destroy<_Fun>, false,
+#ifndef _LIBCPP_NO_RTTI
+          &typeid(typename _Fun::_Target)
+#else
+          nullptr
+#endif
+      };
+        return &__policy_;
+    }
+
+    template <typename _Fun>
+    _LIBCPP_INLINE_VISIBILITY static const __policy*
+        __choose_policy(/* is_small = */ true_type)
+    {
+        static const _LIBCPP_CONSTEXPR __policy __policy_ = {
+            nullptr, nullptr, false,
+#ifndef _LIBCPP_NO_RTTI
+            &typeid(typename _Fun::_Target)
+#else
+            nullptr
+#endif
+        };
+        return &__policy_;
+    }
+};
+
+// Used to choose between perfect forwarding or pass-by-value. Pass-by-value is
+// faster for types that can be passed in registers.
+template <typename _Tp>
+using __fast_forward =
+    typename conditional<is_scalar<_Tp>::value, _Tp, _Tp&&>::type;
+
+// __policy_invoker calls an instance of __alloc_func held in __policy_storage.
+
+template <class _Fp> struct __policy_invoker;
+
+template <class _Rp, class... _ArgTypes>
+struct __policy_invoker<_Rp(_ArgTypes...)>
+{
+    typedef _Rp (*__Call)(const __policy_storage*,
+                          __fast_forward<_ArgTypes>...);
+
+    __Call __call_;
+
+    // Creates an invoker that throws bad_function_call.
+    _LIBCPP_INLINE_VISIBILITY
+    __policy_invoker() : __call_(&__call_empty) {}
+
+    // Creates an invoker that calls the given instance of __func.
+    template <typename _Fun>
+    _LIBCPP_INLINE_VISIBILITY static __policy_invoker __create()
+    {
+        return __policy_invoker(&__call_impl<_Fun>);
+    }
+
+  private:
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __policy_invoker(__Call __c) : __call_(__c) {}
+
+    static _Rp __call_empty(const __policy_storage*,
+                            __fast_forward<_ArgTypes>...)
+    {
+        __throw_bad_function_call();
+    }
+
+    template <typename _Fun>
+    static _Rp __call_impl(const __policy_storage* __buf,
+                           __fast_forward<_ArgTypes>... __args)
+    {
+        _Fun* __f = reinterpret_cast<_Fun*>(__use_small_storage<_Fun>::value
+                                                ? &__buf->__small
+                                                : __buf->__large);
+        return (*__f)(_VSTD::forward<_ArgTypes>(__args)...);
+    }
+};
+
+// __policy_func uses a __policy and __policy_invoker to create a type-erased,
+// copyable functor.
+
+template <class _Fp> class __policy_func;
+
+template <class _Rp, class... _ArgTypes> class __policy_func<_Rp(_ArgTypes...)>
+{
+    // Inline storage for small objects.
+    __policy_storage __buf_;
+
+    // Calls the value stored in __buf_. This could technically be part of
+    // policy, but storing it here eliminates a level of indirection inside
+    // operator().
+    typedef __function::__policy_invoker<_Rp(_ArgTypes...)> __invoker;
+    __invoker __invoker_;
+
+    // The policy that describes how to move / copy / destroy __buf_. Never
+    // null, even if the function is empty.
+    const __policy* __policy_;
+
+  public:
+    _LIBCPP_INLINE_VISIBILITY
+    __policy_func() : __policy_(__policy::__create_empty()) {}
+
+    template <class _Fp, class _Alloc>
+    _LIBCPP_INLINE_VISIBILITY __policy_func(_Fp&& __f, const _Alloc& __a)
+        : __policy_(__policy::__create_empty())
+    {
+        typedef __alloc_func<_Fp, _Alloc, _Rp(_ArgTypes...)> _Fun;
+        typedef allocator_traits<_Alloc> __alloc_traits;
+        typedef typename __rebind_alloc_helper<__alloc_traits, _Fun>::type
+            _FunAlloc;
+
+        if (__function::__not_null(__f))
+        {
+            __invoker_ = __invoker::template __create<_Fun>();
+            __policy_ = __policy::__create<_Fun>();
+
+            _FunAlloc __af(__a);
+            if (__use_small_storage<_Fun>())
+            {
+                ::new ((void*)&__buf_.__small)
+                    _Fun(_VSTD::move(__f), _Alloc(__af));
+            }
+            else
+            {
+                typedef __allocator_destructor<_FunAlloc> _Dp;
+                unique_ptr<_Fun, _Dp> __hold(__af.allocate(1), _Dp(__af, 1));
+                ::new ((void*)__hold.get())
+                    _Fun(_VSTD::move(__f), _Alloc(__af));
+                __buf_.__large = __hold.release();
+            }
+        }
+    }
+
+    template <class _Fp, class = typename enable_if<!is_same<typename decay<_Fp>::type, __policy_func>::value>::type>
+    _LIBCPP_INLINE_VISIBILITY explicit __policy_func(_Fp&& __f)
+        : __policy_(__policy::__create_empty()) {
+      typedef __default_alloc_func<_Fp, _Rp(_ArgTypes...)> _Fun;
+
+      if (__function::__not_null(__f)) {
+        __invoker_ = __invoker::template __create<_Fun>();
+        __policy_ = __policy::__create<_Fun>();
+        if (__use_small_storage<_Fun>()) {
+          ::new ((void*)&__buf_.__small) _Fun(_VSTD::move(__f));
+        } else {
+          __builtin_new_allocator::__holder_t __hold =
+              __builtin_new_allocator::__allocate_type<_Fun>(1);
+          __buf_.__large = ::new ((void*)__hold.get()) _Fun(_VSTD::move(__f));
+          (void)__hold.release();
+        }
+      }
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __policy_func(const __policy_func& __f)
+        : __buf_(__f.__buf_), __invoker_(__f.__invoker_),
+          __policy_(__f.__policy_)
+    {
+        if (__policy_->__clone)
+            __buf_.__large = __policy_->__clone(__f.__buf_.__large);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __policy_func(__policy_func&& __f)
+        : __buf_(__f.__buf_), __invoker_(__f.__invoker_),
+          __policy_(__f.__policy_)
+    {
+        if (__policy_->__destroy)
+        {
+            __f.__policy_ = __policy::__create_empty();
+            __f.__invoker_ = __invoker();
+        }
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    ~__policy_func()
+    {
+        if (__policy_->__destroy)
+            __policy_->__destroy(__buf_.__large);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __policy_func& operator=(__policy_func&& __f)
+    {
+        *this = nullptr;
+        __buf_ = __f.__buf_;
+        __invoker_ = __f.__invoker_;
+        __policy_ = __f.__policy_;
+        __f.__policy_ = __policy::__create_empty();
+        __f.__invoker_ = __invoker();
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __policy_func& operator=(nullptr_t)
+    {
+        const __policy* __p = __policy_;
+        __policy_ = __policy::__create_empty();
+        __invoker_ = __invoker();
+        if (__p->__destroy)
+            __p->__destroy(__buf_.__large);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    _Rp operator()(_ArgTypes&&... __args) const
+    {
+        return __invoker_.__call_(_VSTD::addressof(__buf_),
+                                  _VSTD::forward<_ArgTypes>(__args)...);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void swap(__policy_func& __f)
+    {
+        _VSTD::swap(__invoker_, __f.__invoker_);
+        _VSTD::swap(__policy_, __f.__policy_);
+        _VSTD::swap(__buf_, __f.__buf_);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit operator bool() const _NOEXCEPT
+    {
+        return !__policy_->__is_null;
+    }
+
+#ifndef _LIBCPP_NO_RTTI
+    _LIBCPP_INLINE_VISIBILITY
+    const std::type_info& target_type() const _NOEXCEPT
+    {
+        return *__policy_->__type_info;
+    }
+
+    template <typename _Tp>
+    _LIBCPP_INLINE_VISIBILITY const _Tp* target() const _NOEXCEPT
+    {
+        if (__policy_->__is_null || typeid(_Tp) != *__policy_->__type_info)
+            return nullptr;
+        if (__policy_->__clone) // Out of line storage.
+            return reinterpret_cast<const _Tp*>(__buf_.__large);
+        else
+            return reinterpret_cast<const _Tp*>(&__buf_.__small);
+    }
+#endif // _LIBCPP_NO_RTTI
+};
+
+#if defined(_LIBCPP_HAS_BLOCKS_RUNTIME) && !defined(_LIBCPP_HAS_OBJC_ARC)
+
+extern "C" void *_Block_copy(const void *);
+extern "C" void _Block_release(const void *);
+
+template<class _Rp1, class ..._ArgTypes1, class _Alloc, class _Rp, class ..._ArgTypes>
+class __func<_Rp1(^)(_ArgTypes1...), _Alloc, _Rp(_ArgTypes...)>
+    : public  __base<_Rp(_ArgTypes...)>
+{
+    typedef _Rp1(^__block_type)(_ArgTypes1...);
+    __block_type __f_;
+
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __func(__block_type const& __f)
+        : __f_(reinterpret_cast<__block_type>(__f ? _Block_copy(__f) : nullptr))
+    { }
+
+    // [TODO] add && to save on a retain
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit __func(__block_type __f, const _Alloc& /* unused */)
+        : __f_(reinterpret_cast<__block_type>(__f ? _Block_copy(__f) : nullptr))
+    { }
+
+    virtual __base<_Rp(_ArgTypes...)>* __clone() const {
+        _LIBCPP_ASSERT(false,
+            "Block pointers are just pointers, so they should always fit into "
+            "std::function's small buffer optimization. This function should "
+            "never be invoked.");
+        return nullptr;
+    }
+
+    virtual void __clone(__base<_Rp(_ArgTypes...)>* __p) const {
+        ::new ((void*)__p) __func(__f_);
+    }
+
+    virtual void destroy() _NOEXCEPT {
+        if (__f_)
+            _Block_release(__f_);
+        __f_ = 0;
+    }
+
+    virtual void destroy_deallocate() _NOEXCEPT {
+        _LIBCPP_ASSERT(false,
+            "Block pointers are just pointers, so they should always fit into "
+            "std::function's small buffer optimization. This function should "
+            "never be invoked.");
+    }
+
+    virtual _Rp operator()(_ArgTypes&& ... __arg) {
+        return _VSTD::__invoke(__f_, _VSTD::forward<_ArgTypes>(__arg)...);
+    }
+
+#ifndef _LIBCPP_NO_RTTI
+    virtual const void* target(type_info const& __ti) const _NOEXCEPT {
+        if (__ti == typeid(__func::__block_type))
+            return &__f_;
+        return (const void*)nullptr;
+    }
+
+    virtual const std::type_info& target_type() const _NOEXCEPT {
+        return typeid(__func::__block_type);
+    }
+#endif // _LIBCPP_NO_RTTI
+};
+
+#endif // _LIBCPP_HAS_EXTENSION_BLOCKS && !_LIBCPP_HAS_OBJC_ARC
+
+}  // __function
+
+template<class _Rp, class ..._ArgTypes>
+class _LIBCPP_TEMPLATE_VIS function<_Rp(_ArgTypes...)>
+#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : public __function::__maybe_derive_from_unary_function<_Rp(_ArgTypes...)>,
+      public __function::__maybe_derive_from_binary_function<_Rp(_ArgTypes...)>
+#endif
+{
+#ifndef _LIBCPP_ABI_OPTIMIZED_FUNCTION
+    typedef __function::__value_func<_Rp(_ArgTypes...)> __func;
+#else
+    typedef __function::__policy_func<_Rp(_ArgTypes...)> __func;
+#endif
+
+    __func __f_;
+
+    template <class _Fp, bool = _And<
+        _IsNotSame<__uncvref_t<_Fp>, function>,
+        __invokable<_Fp, _ArgTypes...>
+    >::value>
+    struct __callable;
+    template <class _Fp>
+        struct __callable<_Fp, true>
+        {
+            static const bool value = is_void<_Rp>::value ||
+                __is_core_convertible<typename __invoke_of<_Fp, _ArgTypes...>::type,
+                                      _Rp>::value;
+        };
+    template <class _Fp>
+        struct __callable<_Fp, false>
+        {
+            static const bool value = false;
+        };
+
+  template <class _Fp>
+  using _EnableIfLValueCallable = typename enable_if<__callable<_Fp&>::value>::type;
+public:
+    typedef _Rp result_type;
+
+    // construct/copy/destroy:
+    _LIBCPP_INLINE_VISIBILITY
+    function() _NOEXCEPT { }
+    _LIBCPP_INLINE_VISIBILITY
+    function(nullptr_t) _NOEXCEPT {}
+    function(const function&);
+    function(function&&) _NOEXCEPT;
+    template<class _Fp, class = _EnableIfLValueCallable<_Fp>>
+    function(_Fp);
+
+#if _LIBCPP_STD_VER <= 14
+    template<class _Alloc>
+      _LIBCPP_INLINE_VISIBILITY
+      function(allocator_arg_t, const _Alloc&) _NOEXCEPT {}
+    template<class _Alloc>
+      _LIBCPP_INLINE_VISIBILITY
+      function(allocator_arg_t, const _Alloc&, nullptr_t) _NOEXCEPT {}
+    template<class _Alloc>
+      function(allocator_arg_t, const _Alloc&, const function&);
+    template<class _Alloc>
+      function(allocator_arg_t, const _Alloc&, function&&);
+    template<class _Fp, class _Alloc, class = _EnableIfLValueCallable<_Fp>>
+      function(allocator_arg_t, const _Alloc& __a, _Fp __f);
+#endif
+
+    function& operator=(const function&);
+    function& operator=(function&&) _NOEXCEPT;
+    function& operator=(nullptr_t) _NOEXCEPT;
+    template<class _Fp, class = _EnableIfLValueCallable<typename decay<_Fp>::type>>
+    function& operator=(_Fp&&);
+
+    ~function();
+
+    // function modifiers:
+    void swap(function&) _NOEXCEPT;
+
+#if _LIBCPP_STD_VER <= 14
+    template<class _Fp, class _Alloc>
+      _LIBCPP_INLINE_VISIBILITY
+      void assign(_Fp&& __f, const _Alloc& __a)
+        {function(allocator_arg, __a, _VSTD::forward<_Fp>(__f)).swap(*this);}
+#endif
+
+    // function capacity:
+    _LIBCPP_INLINE_VISIBILITY
+    explicit operator bool() const _NOEXCEPT {
+      return static_cast<bool>(__f_);
+    }
+
+    // deleted overloads close possible hole in the type system
+    template<class _R2, class... _ArgTypes2>
+      bool operator==(const function<_R2(_ArgTypes2...)>&) const = delete;
+    template<class _R2, class... _ArgTypes2>
+      bool operator!=(const function<_R2(_ArgTypes2...)>&) const = delete;
+public:
+    // function invocation:
+    _Rp operator()(_ArgTypes...) const;
+
+#ifndef _LIBCPP_NO_RTTI
+    // function target access:
+    const std::type_info& target_type() const _NOEXCEPT;
+    template <typename _Tp> _Tp* target() _NOEXCEPT;
+    template <typename _Tp> const _Tp* target() const _NOEXCEPT;
+#endif // _LIBCPP_NO_RTTI
+};
+
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _Rp, class ..._Ap>
+function(_Rp(*)(_Ap...)) -> function<_Rp(_Ap...)>;
+
+template<class _Fp>
+struct __strip_signature;
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...)> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile> { using type = _Rp(_Ap...); };
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) &> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const &> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile &> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile &> { using type = _Rp(_Ap...); };
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile noexcept> { using type = _Rp(_Ap...); };
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) & noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const & noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile & noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile & noexcept> { using type = _Rp(_Ap...); };
+
+template<class _Fp, class _Stripped = typename __strip_signature<decltype(&_Fp::operator())>::type>
+function(_Fp) -> function<_Stripped>;
+#endif // !_LIBCPP_HAS_NO_DEDUCTION_GUIDES
+
+template<class _Rp, class ..._ArgTypes>
+function<_Rp(_ArgTypes...)>::function(const function& __f) : __f_(__f.__f_) {}
+
+#if _LIBCPP_STD_VER <= 14
+template<class _Rp, class ..._ArgTypes>
+template <class _Alloc>
+function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
+                                     const function& __f) : __f_(__f.__f_) {}
+#endif
+
+template <class _Rp, class... _ArgTypes>
+function<_Rp(_ArgTypes...)>::function(function&& __f) _NOEXCEPT
+    : __f_(_VSTD::move(__f.__f_)) {}
+
+#if _LIBCPP_STD_VER <= 14
+template<class _Rp, class ..._ArgTypes>
+template <class _Alloc>
+function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
+                                      function&& __f)
+    : __f_(_VSTD::move(__f.__f_)) {}
+#endif
+
+template <class _Rp, class... _ArgTypes>
+template <class _Fp, class>
+function<_Rp(_ArgTypes...)>::function(_Fp __f) : __f_(_VSTD::move(__f)) {}
+
+#if _LIBCPP_STD_VER <= 14
+template <class _Rp, class... _ArgTypes>
+template <class _Fp, class _Alloc, class>
+function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc& __a,
+                                      _Fp __f)
+    : __f_(_VSTD::move(__f), __a) {}
+#endif
+
+template<class _Rp, class ..._ArgTypes>
+function<_Rp(_ArgTypes...)>&
+function<_Rp(_ArgTypes...)>::operator=(const function& __f)
+{
+    function(__f).swap(*this);
+    return *this;
+}
+
+template<class _Rp, class ..._ArgTypes>
+function<_Rp(_ArgTypes...)>&
+function<_Rp(_ArgTypes...)>::operator=(function&& __f) _NOEXCEPT
+{
+    __f_ = _VSTD::move(__f.__f_);
+    return *this;
+}
+
+template<class _Rp, class ..._ArgTypes>
+function<_Rp(_ArgTypes...)>&
+function<_Rp(_ArgTypes...)>::operator=(nullptr_t) _NOEXCEPT
+{
+    __f_ = nullptr;
+    return *this;
+}
+
+template<class _Rp, class ..._ArgTypes>
+template <class _Fp, class>
+function<_Rp(_ArgTypes...)>&
+function<_Rp(_ArgTypes...)>::operator=(_Fp&& __f)
+{
+    function(_VSTD::forward<_Fp>(__f)).swap(*this);
+    return *this;
+}
+
+template<class _Rp, class ..._ArgTypes>
+function<_Rp(_ArgTypes...)>::~function() {}
+
+template<class _Rp, class ..._ArgTypes>
+void
+function<_Rp(_ArgTypes...)>::swap(function& __f) _NOEXCEPT
+{
+    __f_.swap(__f.__f_);
+}
+
+template<class _Rp, class ..._ArgTypes>
+_Rp
+function<_Rp(_ArgTypes...)>::operator()(_ArgTypes... __arg) const
+{
+    return __f_(_VSTD::forward<_ArgTypes>(__arg)...);
+}
+
+#ifndef _LIBCPP_NO_RTTI
+
+template<class _Rp, class ..._ArgTypes>
+const std::type_info&
+function<_Rp(_ArgTypes...)>::target_type() const _NOEXCEPT
+{
+    return __f_.target_type();
+}
+
+template<class _Rp, class ..._ArgTypes>
+template <typename _Tp>
+_Tp*
+function<_Rp(_ArgTypes...)>::target() _NOEXCEPT
+{
+    return (_Tp*)(__f_.template target<_Tp>());
+}
+
+template<class _Rp, class ..._ArgTypes>
+template <typename _Tp>
+const _Tp*
+function<_Rp(_ArgTypes...)>::target() const _NOEXCEPT
+{
+    return __f_.template target<_Tp>();
+}
+
+#endif // _LIBCPP_NO_RTTI
+
+template <class _Rp, class... _ArgTypes>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const function<_Rp(_ArgTypes...)>& __f, nullptr_t) _NOEXCEPT {return !__f;}
+
+template <class _Rp, class... _ArgTypes>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(nullptr_t, const function<_Rp(_ArgTypes...)>& __f) _NOEXCEPT {return !__f;}
+
+template <class _Rp, class... _ArgTypes>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const function<_Rp(_ArgTypes...)>& __f, nullptr_t) _NOEXCEPT {return (bool)__f;}
+
+template <class _Rp, class... _ArgTypes>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(nullptr_t, const function<_Rp(_ArgTypes...)>& __f) _NOEXCEPT {return (bool)__f;}
+
+template <class _Rp, class... _ArgTypes>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+swap(function<_Rp(_ArgTypes...)>& __x, function<_Rp(_ArgTypes...)>& __y) _NOEXCEPT
+{return __x.swap(__y);}
+
+#else // _LIBCPP_CXX03_LANG
+
 namespace __function {
 
 template<class _Fp> class __base;
 
 template<class _Rp>
 class __base<_Rp()>
 {
     __base(const __base&);

 operator!=(nullptr_t, const function<_Fp>& __f) {return (bool)__f;}
 
 template <class _Fp>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 swap(function<_Fp>& __x, function<_Fp>& __y)
 {return __x.swap(__y);}
 
-#endif // _LIBCPP_FUNCTIONAL_03
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_FUNCTION_H

libcxx/include/__functional/greater.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_GREATER_H
+#define _LIBCPP___FUNCTIONAL_GREATER_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS greater
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x > __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS greater<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) > _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) > _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) > _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_GREATER_H

libcxx/include/__functional/greater_equal.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_GREATER_EQUAL_H
+#define _LIBCPP___FUNCTIONAL_GREATER_EQUAL_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS greater_equal
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x >= __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS greater_equal<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) >= _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) >= _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) >= _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_GREATER_EQUAL_H

libcxx/include/__functional/identity.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_IDENTITY_H
+#define _LIBCPP___FUNCTIONAL_IDENTITY_H
+
+#include <__config>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17
+
+struct identity {
+    template<class _Tp>
+    _LIBCPP_NODISCARD_EXT constexpr _Tp&& operator()(_Tp&& __t) const noexcept
+    {
+        return _VSTD::forward<_Tp>(__t);
+    }
+
+    using is_transparent = void;
+};
+#endif // _LIBCPP_STD_VER > 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_IDENTITY_H

libcxx/include/__functional/invoke.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_INVOKE_H
+#define _LIBCPP___FUNCTIONAL_INVOKE_H
+
+#include <__config>
+#include <__functional/weak_result_type.h>
+#include <__utility/forward.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Ret, bool = is_void<_Ret>::value>
+struct __invoke_void_return_wrapper
+{
+#ifndef _LIBCPP_CXX03_LANG
+    template <class ..._Args>
+    static _Ret __call(_Args&&... __args) {
+        return _VSTD::__invoke(_VSTD::forward<_Args>(__args)...);
+    }
+#else
+    template <class _Fn>
+    static _Ret __call(_Fn __f) {
+        return _VSTD::__invoke(__f);
+    }
+
+    template <class _Fn, class _A0>
+    static _Ret __call(_Fn __f, _A0& __a0) {
+        return _VSTD::__invoke(__f, __a0);
+    }
+
+    template <class _Fn, class _A0, class _A1>
+    static _Ret __call(_Fn __f, _A0& __a0, _A1& __a1) {
+        return _VSTD::__invoke(__f, __a0, __a1);
+    }
+
+    template <class _Fn, class _A0, class _A1, class _A2>
+    static _Ret __call(_Fn __f, _A0& __a0, _A1& __a1, _A2& __a2){
+        return _VSTD::__invoke(__f, __a0, __a1, __a2);
+    }
+#endif
+};
+
+template <class _Ret>
+struct __invoke_void_return_wrapper<_Ret, true>
+{
+#ifndef _LIBCPP_CXX03_LANG
+    template <class ..._Args>
+    static void __call(_Args&&... __args) {
+        _VSTD::__invoke(_VSTD::forward<_Args>(__args)...);
+    }
+#else
+    template <class _Fn>
+    static void __call(_Fn __f) {
+        _VSTD::__invoke(__f);
+    }
+
+    template <class _Fn, class _A0>
+    static void __call(_Fn __f, _A0& __a0) {
+        _VSTD::__invoke(__f, __a0);
+    }
+
+    template <class _Fn, class _A0, class _A1>
+    static void __call(_Fn __f, _A0& __a0, _A1& __a1) {
+        _VSTD::__invoke(__f, __a0, __a1);
+    }
+
+    template <class _Fn, class _A0, class _A1, class _A2>
+    static void __call(_Fn __f, _A0& __a0, _A1& __a1, _A2& __a2) {
+        _VSTD::__invoke(__f, __a0, __a1, __a2);
+    }
+#endif
+};
+
+#if _LIBCPP_STD_VER > 14
+
+template <class _Fn, class ..._Args>
+_LIBCPP_CONSTEXPR_AFTER_CXX17 invoke_result_t<_Fn, _Args...>
+invoke(_Fn&& __f, _Args&&... __args)
+    noexcept(is_nothrow_invocable_v<_Fn, _Args...>)
+{
+    return _VSTD::__invoke(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)...);
+}
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_INVOKE_H

libcxx/include/__functional/is_transparent.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_IS_TRANSPARENT
+#define _LIBCPP___FUNCTIONAL_IS_TRANSPARENT
+
+#include <__config>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 11
+
+template <class _Tp, class, class = void>
+struct __is_transparent : false_type {};
+
+template <class _Tp, class _Up>
+struct __is_transparent<_Tp, _Up,
+                        typename __void_t<typename _Tp::is_transparent>::type>
+   : true_type {};
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_IS_TRANSPARENT

libcxx/include/__functional/less.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_LESS_H
+#define _LIBCPP___FUNCTIONAL_LESS_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS less
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x < __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS less<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) < _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) < _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) < _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_LESS_H

libcxx/include/__functional/less_equal.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_LESS_EQUAL_H
+#define _LIBCPP___FUNCTIONAL_LESS_EQUAL_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS less_equal
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x <= __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS less_equal<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) <= _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) <= _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) <= _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_LESS_EQUAL_H

libcxx/include/__functional/logical_and.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_LOGICAL_AND_H
+#define _LIBCPP___FUNCTIONAL_LOGICAL_AND_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS logical_and
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x && __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS logical_and<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) && _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) && _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) && _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_LOGICAL_AND_H

libcxx/include/__functional/logical_not.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_LOGICAL_NOT_H
+#define _LIBCPP___FUNCTIONAL_LOGICAL_NOT_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS logical_not
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : unary_function<_Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x) const
+        {return !__x;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS logical_not<void>
+{
+    template <class _Tp>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_Tp&& __x) const
+    _NOEXCEPT_(noexcept(!_VSTD::forward<_Tp>(__x)))
+    -> decltype        (!_VSTD::forward<_Tp>(__x))
+        { return        !_VSTD::forward<_Tp>(__x); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_LOGICAL_NOT_H

libcxx/include/__functional/logical_or.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_LOGICAL_OR_H
+#define _LIBCPP___FUNCTIONAL_LOGICAL_OR_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS logical_or
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x || __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS logical_or<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) || _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) || _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) || _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_LOGICAL_OR_H

libcxx/include/__functional/mem_fn.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_MEM_FN_H
+#define _LIBCPP___FUNCTIONAL_MEM_FN_H
+
+#include <__config>
+#include <__functional/weak_result_type.h>
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+class __mem_fn
+#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : public __weak_result_type<_Tp>
+#endif
+{
+public:
+    // types
+    typedef _Tp type;
+private:
+    type __f_;
+
+public:
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    __mem_fn(type __f) _NOEXCEPT : __f_(__f) {}
+
+#ifndef _LIBCPP_CXX03_LANG
+    // invoke
+    template <class... _ArgTypes>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    typename __invoke_return<type, _ArgTypes...>::type
+    operator() (_ArgTypes&&... __args) const {
+        return _VSTD::__invoke(__f_, _VSTD::forward<_ArgTypes>(__args)...);
+    }
+#else
+
+    template <class _A0>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return0<type, _A0>::type
+    operator() (_A0& __a0) const {
+        return _VSTD::__invoke(__f_, __a0);
+    }
+
+    template <class _A0>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return0<type, _A0 const>::type
+    operator() (_A0 const& __a0) const {
+        return _VSTD::__invoke(__f_, __a0);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0, _A1>::type
+    operator() (_A0& __a0, _A1& __a1) const {
+        return _VSTD::__invoke(__f_, __a0, __a1);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0 const, _A1>::type
+    operator() (_A0 const& __a0, _A1& __a1) const {
+        return _VSTD::__invoke(__f_, __a0, __a1);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0, _A1 const>::type
+    operator() (_A0& __a0, _A1 const& __a1) const {
+        return _VSTD::__invoke(__f_, __a0, __a1);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0 const, _A1 const>::type
+    operator() (_A0 const& __a0, _A1 const& __a1) const {
+        return _VSTD::__invoke(__f_, __a0, __a1);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1, _A2>::type
+    operator() (_A0& __a0, _A1& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1, _A2>::type
+    operator() (_A0 const& __a0, _A1& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1 const, _A2>::type
+    operator() (_A0& __a0, _A1 const& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1, _A2 const>::type
+    operator() (_A0& __a0, _A1& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1 const, _A2>::type
+    operator() (_A0 const& __a0, _A1 const& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1, _A2 const>::type
+    operator() (_A0 const& __a0, _A1& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1 const, _A2 const>::type
+    operator() (_A0& __a0, _A1 const& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1 const, _A2 const>::type
+    operator() (_A0 const& __a0, _A1 const& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
+    }
+#endif
+};
+
+template<class _Rp, class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+__mem_fn<_Rp _Tp::*>
+mem_fn(_Rp _Tp::* __pm) _NOEXCEPT
+{
+    return __mem_fn<_Rp _Tp::*>(__pm);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_MEM_FN_H

libcxx/include/__functional/mem_fun_ref.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_MEM_FUN_REF_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_MEM_FUN_REF_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+#include <__functional/binary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+template<class _Sp, class _Tp>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun_t
+    : public unary_function<_Tp*, _Sp>
+{
+    _Sp (_Tp::*__p_)();
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit mem_fun_t(_Sp (_Tp::*__p)())
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp* __p) const
+        {return (__p->*__p_)();}
+};
+
+template<class _Sp, class _Tp, class _Ap>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun1_t
+    : public binary_function<_Tp*, _Ap, _Sp>
+{
+    _Sp (_Tp::*__p_)(_Ap);
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit mem_fun1_t(_Sp (_Tp::*__p)(_Ap))
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp* __p, _Ap __x) const
+        {return (__p->*__p_)(__x);}
+};
+
+template<class _Sp, class _Tp>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+mem_fun_t<_Sp,_Tp>
+mem_fun(_Sp (_Tp::*__f)())
+    {return mem_fun_t<_Sp,_Tp>(__f);}
+
+template<class _Sp, class _Tp, class _Ap>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+mem_fun1_t<_Sp,_Tp,_Ap>
+mem_fun(_Sp (_Tp::*__f)(_Ap))
+    {return mem_fun1_t<_Sp,_Tp,_Ap>(__f);}
+
+template<class _Sp, class _Tp>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun_ref_t
+    : public unary_function<_Tp, _Sp>
+{
+    _Sp (_Tp::*__p_)();
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit mem_fun_ref_t(_Sp (_Tp::*__p)())
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp& __p) const
+        {return (__p.*__p_)();}
+};
+
+template<class _Sp, class _Tp, class _Ap>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun1_ref_t
+    : public binary_function<_Tp, _Ap, _Sp>
+{
+    _Sp (_Tp::*__p_)(_Ap);
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit mem_fun1_ref_t(_Sp (_Tp::*__p)(_Ap))
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp& __p, _Ap __x) const
+        {return (__p.*__p_)(__x);}
+};
+
+template<class _Sp, class _Tp>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+mem_fun_ref_t<_Sp,_Tp>
+mem_fun_ref(_Sp (_Tp::*__f)())
+    {return mem_fun_ref_t<_Sp,_Tp>(__f);}
+
+template<class _Sp, class _Tp, class _Ap>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+mem_fun1_ref_t<_Sp,_Tp,_Ap>
+mem_fun_ref(_Sp (_Tp::*__f)(_Ap))
+    {return mem_fun1_ref_t<_Sp,_Tp,_Ap>(__f);}
+
+template <class _Sp, class _Tp>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun_t
+    : public unary_function<const _Tp*, _Sp>
+{
+    _Sp (_Tp::*__p_)() const;
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun_t(_Sp (_Tp::*__p)() const)
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp* __p) const
+        {return (__p->*__p_)();}
+};
+
+template <class _Sp, class _Tp, class _Ap>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun1_t
+    : public binary_function<const _Tp*, _Ap, _Sp>
+{
+    _Sp (_Tp::*__p_)(_Ap) const;
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun1_t(_Sp (_Tp::*__p)(_Ap) const)
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp* __p, _Ap __x) const
+        {return (__p->*__p_)(__x);}
+};
+
+template <class _Sp, class _Tp>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+const_mem_fun_t<_Sp,_Tp>
+mem_fun(_Sp (_Tp::*__f)() const)
+    {return const_mem_fun_t<_Sp,_Tp>(__f);}
+
+template <class _Sp, class _Tp, class _Ap>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+const_mem_fun1_t<_Sp,_Tp,_Ap>
+mem_fun(_Sp (_Tp::*__f)(_Ap) const)
+    {return const_mem_fun1_t<_Sp,_Tp,_Ap>(__f);}
+
+template <class _Sp, class _Tp>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun_ref_t
+    : public unary_function<_Tp, _Sp>
+{
+    _Sp (_Tp::*__p_)() const;
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun_ref_t(_Sp (_Tp::*__p)() const)
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp& __p) const
+        {return (__p.*__p_)();}
+};
+
+template <class _Sp, class _Tp, class _Ap>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun1_ref_t
+    : public binary_function<_Tp, _Ap, _Sp>
+{
+    _Sp (_Tp::*__p_)(_Ap) const;
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun1_ref_t(_Sp (_Tp::*__p)(_Ap) const)
+        : __p_(__p) {}
+    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp& __p, _Ap __x) const
+        {return (__p.*__p_)(__x);}
+};
+
+template <class _Sp, class _Tp>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+const_mem_fun_ref_t<_Sp,_Tp>
+mem_fun_ref(_Sp (_Tp::*__f)() const)
+    {return const_mem_fun_ref_t<_Sp,_Tp>(__f);}
+
+template <class _Sp, class _Tp, class _Ap>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+const_mem_fun1_ref_t<_Sp,_Tp,_Ap>
+mem_fun_ref(_Sp (_Tp::*__f)(_Ap) const)
+    {return const_mem_fun1_ref_t<_Sp,_Tp,_Ap>(__f);}
+
+#endif // _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_MEM_FUN_REF_H

libcxx/include/__functional/minus.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_MINUS_H
+#define _LIBCPP___FUNCTIONAL_MINUS_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS minus
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x - __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS minus<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) - _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) - _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) - _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_MINUS_H

libcxx/include/__functional/modulus.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_MODULUS_H
+#define _LIBCPP___FUNCTIONAL_MODULUS_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS modulus
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x % __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS modulus<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) % _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) % _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) % _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_MODULUS_H

libcxx/include/__functional/multiplies.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_MULTIPLIES_H
+#define _LIBCPP___FUNCTIONAL_MULTIPLIES_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS multiplies
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x * __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS multiplies<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) * _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) * _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) * _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_MULTIPLIES_H

libcxx/include/__functional/negate.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_NEGATE_H
+#define _LIBCPP___FUNCTIONAL_NEGATE_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS negate
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : unary_function<_Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x) const
+        {return -__x;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS negate<void>
+{
+    template <class _Tp>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_Tp&& __x) const
+    _NOEXCEPT_(noexcept(- _VSTD::forward<_Tp>(__x)))
+    -> decltype        (- _VSTD::forward<_Tp>(__x))
+        { return        - _VSTD::forward<_Tp>(__x); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_NEGATE_H

libcxx/include/__functional/not_equal_to.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_NOT_EQUAL_TO_H
+#define _LIBCPP___FUNCTIONAL_NOT_EQUAL_TO_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS not_equal_to
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, bool>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef bool __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x != __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS not_equal_to<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) != _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) != _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) != _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_NOT_EQUAL_TO_H

libcxx/include/__functional/not_fn.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_NOT_FN_H
+#define _LIBCPP___FUNCTIONAL_NOT_FN_H
+
+#include <__config>
+#include <__functional/perfect_forward.h>
+#include <__functional/invoke.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+struct __not_fn_op
+{
+    template<class... _Args>
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17 auto __call(_Args&&... __args)
+    noexcept(noexcept(!_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
+    -> decltype(      !_VSTD::invoke(_VSTD::forward<_Args>(__args)...))
+    { return          !_VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
+};
+
+template<class _Fn,
+         class = _EnableIf<is_constructible_v<decay_t<_Fn>, _Fn> &&
+                           is_move_constructible_v<_Fn>>>
+_LIBCPP_CONSTEXPR_AFTER_CXX17 auto not_fn(_Fn&& __f)
+{
+    return __perfect_forward<__not_fn_op, _Fn>(_VSTD::forward<_Fn>(__f));
+}
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_NOT_FN_H

libcxx/include/__functional/perfect_forward.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H
+#define _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H
+
+#include <__config>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+template<class _Op, class _Tuple,
+         class _Idxs = typename __make_tuple_indices<tuple_size<_Tuple>::value>::type>
+struct __perfect_forward_impl;
+
+template<class _Op, class... _Bound, size_t... _Idxs>
+struct __perfect_forward_impl<_Op, __tuple_types<_Bound...>, __tuple_indices<_Idxs...>>
+{
+    tuple<_Bound...> __bound_;
+
+    template<class... _Args>
+    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) &
+    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...)))
+    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...))
+    {return           _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...);}
+
+    template<class... _Args>
+    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) const&
+    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...)))
+    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...))
+    {return           _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...);}
+
+    template<class... _Args>
+    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) &&
+    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
+                                  _VSTD::forward<_Args>(__args)...)))
+    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
+                                  _VSTD::forward<_Args>(__args)...))
+    {return           _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
+                                  _VSTD::forward<_Args>(__args)...);}
+
+    template<class... _Args>
+    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) const&&
+    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
+                                  _VSTD::forward<_Args>(__args)...)))
+    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
+                                  _VSTD::forward<_Args>(__args)...))
+    {return           _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
+                                  _VSTD::forward<_Args>(__args)...);}
+
+    template<class _Fn = typename tuple_element<0, tuple<_Bound...>>::type,
+             class = _EnableIf<is_copy_constructible_v<_Fn>>>
+    constexpr __perfect_forward_impl(__perfect_forward_impl const& __other)
+        : __bound_(__other.__bound_) {}
+
+    template<class _Fn = typename tuple_element<0, tuple<_Bound...>>::type,
+             class = _EnableIf<is_move_constructible_v<_Fn>>>
+    constexpr __perfect_forward_impl(__perfect_forward_impl && __other)
+        : __bound_(_VSTD::move(__other.__bound_)) {}
+
+    template<class... _BoundArgs>
+    explicit constexpr __perfect_forward_impl(_BoundArgs&&... __bound) :
+        __bound_(_VSTD::forward<_BoundArgs>(__bound)...) { }
+};
+
+template<class _Op, class... _Args>
+using __perfect_forward =
+    __perfect_forward_impl<_Op, __tuple_types<decay_t<_Args>...>>;
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H

libcxx/include/__functional/plus.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_PLUS_H
+#define _LIBCPP___FUNCTIONAL_PLUS_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#if _LIBCPP_STD_VER > 11
+template <class _Tp = void>
+#else
+template <class _Tp>
+#endif
+struct _LIBCPP_TEMPLATE_VIS plus
+#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : binary_function<_Tp, _Tp, _Tp>
+#endif
+{
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+    typedef _Tp __result_type;  // used by valarray
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
+    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
+#endif
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(const _Tp& __x, const _Tp& __y) const
+        {return __x + __y;}
+};
+
+#if _LIBCPP_STD_VER > 11
+template <>
+struct _LIBCPP_TEMPLATE_VIS plus<void>
+{
+    template <class _T1, class _T2>
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    auto operator()(_T1&& __t, _T2&& __u) const
+    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u)))
+    -> decltype        (_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u))
+        { return        _VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u); }
+    typedef void is_transparent;
+};
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_PLUS_H

libcxx/include/__functional/pointer_to_binary_function.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_POINTER_TO_BINARY_FUNCTION_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_POINTER_TO_BINARY_FUNCTION_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+template <class _Arg1, class _Arg2, class _Result>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 pointer_to_binary_function
+    : public binary_function<_Arg1, _Arg2, _Result>
+{
+    _Result (*__f_)(_Arg1, _Arg2);
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit pointer_to_binary_function(_Result (*__f)(_Arg1, _Arg2))
+        : __f_(__f) {}
+    _LIBCPP_INLINE_VISIBILITY _Result operator()(_Arg1 __x, _Arg2 __y) const
+        {return __f_(__x, __y);}
+};
+
+template <class _Arg1, class _Arg2, class _Result>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+pointer_to_binary_function<_Arg1,_Arg2,_Result>
+ptr_fun(_Result (*__f)(_Arg1,_Arg2))
+    {return pointer_to_binary_function<_Arg1,_Arg2,_Result>(__f);}
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_POINTER_TO_BINARY_FUNCTION_H

libcxx/include/__functional/pointer_to_unary_function.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_POINTER_TO_UNARY_FUNCTION_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_POINTER_TO_UNARY_FUNCTION_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+template <class _Arg, class _Result>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 pointer_to_unary_function
+    : public unary_function<_Arg, _Result>
+{
+    _Result (*__f_)(_Arg);
+public:
+    _LIBCPP_INLINE_VISIBILITY explicit pointer_to_unary_function(_Result (*__f)(_Arg))
+        : __f_(__f) {}
+    _LIBCPP_INLINE_VISIBILITY _Result operator()(_Arg __x) const
+        {return __f_(__x);}
+};
+
+template <class _Arg, class _Result>
+_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
+pointer_to_unary_function<_Arg,_Result>
+ptr_fun(_Result (*__f)(_Arg))
+    {return pointer_to_unary_function<_Arg,_Result>(__f);}
+
+#endif // _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_POINTER_TO_UNARY_FUNCTION_H

libcxx/include/__functional/ranges/equal_to.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_RANGES_EQUAL_TO_H
+#define _LIBCPP___FUNCTIONAL_RANGES_EQUAL_TO_H
+
+#include <__config>
+#include <concepts>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+namespace ranges {
+
+struct equal_to {
+  template <class _Tp, class _Up>
+  requires equality_comparable_with<_Tp, _Up>
+  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
+      noexcept(noexcept(bool(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u)))) {
+    return _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u);
+  }
+
+  using is_transparent = void;
+};
+
+} // namespace ranges
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_RANGES_EQUAL_TO_H

libcxx/include/__functional/ranges/greater.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_RANGES_GREATER_H
+#define _LIBCPP___FUNCTIONAL_RANGES_GREATER_H
+
+#include <__config>
+#include <concepts>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct greater {
+  template <class _Tp, class _Up>
+  requires totally_ordered_with<_Tp, _Up>
+  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
+      noexcept(noexcept(bool(_VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t)))) {
+    return _VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t);
+  }
+
+  using is_transparent = void;
+};
+} // namespace ranges
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_RANGES_GREATER_H

libcxx/include/__functional/ranges/greater_equal.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_RANGES_GREATER_EQUAL_H
+#define _LIBCPP___FUNCTIONAL_RANGES_GREATER_EQUAL_H
+
+#include <__config>
+#include <concepts>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct greater_equal {
+  template <class _Tp, class _Up>
+  requires totally_ordered_with<_Tp, _Up>
+  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
+      noexcept(noexcept(bool(!(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u))))) {
+    return !(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u));
+  }
+
+  using is_transparent = void;
+};
+} // namespace ranges
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_RANGES_GREATER_EQUAL_H

libcxx/include/__functional/ranges/less.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_RANGES_LESS_H
+#define _LIBCPP___FUNCTIONAL_RANGES_LESS_H
+
+#include <__config>
+#include <concepts>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct less {
+  template <class _Tp, class _Up>
+  requires totally_ordered_with<_Tp, _Up>
+  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
+      noexcept(noexcept(bool(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u)))) {
+    return _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u);
+  }
+
+  using is_transparent = void;
+};
+} // namespace ranges
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_RANGES_LESS_H

libcxx/include/__functional/ranges/less_equal.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_RANGES_LESS_EQUAL_H
+#define _LIBCPP___FUNCTIONAL_RANGES_LESS_EQUAL_H
+
+#include <__config>
+#include <concepts>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct less_equal {
+  template <class _Tp, class _Up>
+  requires totally_ordered_with<_Tp, _Up>
+  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
+      noexcept(noexcept(bool(!(_VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t))))) {
+    return !(_VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t));
+  }
+
+  using is_transparent = void;
+};
+} // namespace ranges
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_RANGES_LESS_EQUAL_H

libcxx/include/__functional/ranges/not_equal_to.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_RANGES_NOT_EQUAL_TO_H
+#define _LIBCPP___FUNCTIONAL_RANGES_NOT_EQUAL_TO_H
+
+#include <__config>
+#include <concepts>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct not_equal_to {
+  template <class _Tp, class _Up>
+  requires equality_comparable_with<_Tp, _Up>
+  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
+      noexcept(noexcept(bool(!(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u))))) {
+    return !(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u));
+  }
+
+  using is_transparent = void;
+};
+} // namespace ranges
+
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_RANGES_NOT_EQUAL_TO_H

libcxx/include/__functional/reference_wrapper.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H
+#define _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H
+
+#include <__config>
+#include <__functional/weak_result_type.h>
+#include <__memory/addressof.h>
+#include <__utility/forward.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+class _LIBCPP_TEMPLATE_VIS reference_wrapper
+#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
+    : public __weak_result_type<_Tp>
+#endif
+{
+public:
+    // types
+    typedef _Tp type;
+private:
+    type* __f_;
+
+#ifndef _LIBCPP_CXX03_LANG
+    static void __fun(_Tp&) _NOEXCEPT;
+    static void __fun(_Tp&&) = delete;
+#endif
+
+public:
+    // construct/copy/destroy
+#ifdef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    reference_wrapper(type& __f) _NOEXCEPT
+        : __f_(_VSTD::addressof(__f)) {}
+#else
+    template <class _Up, class = _EnableIf<!__is_same_uncvref<_Up, reference_wrapper>::value, decltype(__fun(declval<_Up>())) >>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    reference_wrapper(_Up&& __u) _NOEXCEPT_(noexcept(__fun(declval<_Up>()))) {
+        type& __f = static_cast<_Up&&>(__u);
+        __f_ = _VSTD::addressof(__f);
+    }
+#endif
+
+    // access
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    operator type&() const _NOEXCEPT {return *__f_;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    type& get() const _NOEXCEPT {return *__f_;}
+
+#ifndef _LIBCPP_CXX03_LANG
+    // invoke
+    template <class... _ArgTypes>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+    typename __invoke_of<type&, _ArgTypes...>::type
+    operator() (_ArgTypes&&... __args) const {
+        return _VSTD::__invoke(get(), _VSTD::forward<_ArgTypes>(__args)...);
+    }
+#else
+
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return<type>::type
+    operator() () const {
+        return _VSTD::__invoke(get());
+    }
+
+    template <class _A0>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return0<type, _A0>::type
+    operator() (_A0& __a0) const {
+        return _VSTD::__invoke(get(), __a0);
+    }
+
+    template <class _A0>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return0<type, _A0 const>::type
+    operator() (_A0 const& __a0) const {
+        return _VSTD::__invoke(get(), __a0);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0, _A1>::type
+    operator() (_A0& __a0, _A1& __a1) const {
+        return _VSTD::__invoke(get(), __a0, __a1);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0 const, _A1>::type
+    operator() (_A0 const& __a0, _A1& __a1) const {
+        return _VSTD::__invoke(get(), __a0, __a1);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0, _A1 const>::type
+    operator() (_A0& __a0, _A1 const& __a1) const {
+        return _VSTD::__invoke(get(), __a0, __a1);
+    }
+
+    template <class _A0, class _A1>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return1<type, _A0 const, _A1 const>::type
+    operator() (_A0 const& __a0, _A1 const& __a1) const {
+        return _VSTD::__invoke(get(), __a0, __a1);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1, _A2>::type
+    operator() (_A0& __a0, _A1& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1, _A2>::type
+    operator() (_A0 const& __a0, _A1& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1 const, _A2>::type
+    operator() (_A0& __a0, _A1 const& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1, _A2 const>::type
+    operator() (_A0& __a0, _A1& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1 const, _A2>::type
+    operator() (_A0 const& __a0, _A1 const& __a1, _A2& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1, _A2 const>::type
+    operator() (_A0 const& __a0, _A1& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0, _A1 const, _A2 const>::type
+    operator() (_A0& __a0, _A1 const& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+
+    template <class _A0, class _A1, class _A2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename __invoke_return2<type, _A0 const, _A1 const, _A2 const>::type
+    operator() (_A0 const& __a0, _A1 const& __a1, _A2 const& __a2) const {
+        return _VSTD::__invoke(get(), __a0, __a1, __a2);
+    }
+#endif // _LIBCPP_CXX03_LANG
+};
+
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template <class _Tp>
+reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
+#endif
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+reference_wrapper<_Tp>
+ref(_Tp& __t) _NOEXCEPT
+{
+    return reference_wrapper<_Tp>(__t);
+}
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+reference_wrapper<_Tp>
+ref(reference_wrapper<_Tp> __t) _NOEXCEPT
+{
+    return _VSTD::ref(__t.get());
+}
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+reference_wrapper<const _Tp>
+cref(const _Tp& __t) _NOEXCEPT
+{
+    return reference_wrapper<const _Tp>(__t);
+}
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+reference_wrapper<const _Tp>
+cref(reference_wrapper<_Tp> __t) _NOEXCEPT
+{
+    return _VSTD::cref(__t.get());
+}
+
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Tp> void ref(const _Tp&&) = delete;
+template <class _Tp> void cref(const _Tp&&) = delete;
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H

libcxx/include/__functional/unary_negate.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_DEPRECATED_UNARY_NEGATE_H
+#define _LIBCPP___FUNCTIONAL_DEPRECATED_UNARY_NEGATE_H
+
+#include <__config>
+#include <__functional/unary_function.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS)
+
+template <class _Predicate>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 unary_negate
+    : public unary_function<typename _Predicate::argument_type, bool>
+{
+    _Predicate __pred_;
+public:
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    explicit unary_negate(const _Predicate& __pred)
+        : __pred_(__pred) {}
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool operator()(const typename _Predicate::argument_type& __x) const
+        {return !__pred_(__x);}
+};
+
+template <class _Predicate>
+_LIBCPP_DEPRECATED_IN_CXX17 inline _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+unary_negate<_Predicate>
+not1(const _Predicate& __pred) {return unary_negate<_Predicate>(__pred);}
+
+#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_DEPRECATED_UNARY_NEGATE_H

libcxx/include/__functional/unwrap_ref.h

 template <class _Tp>
 struct decay;
 
 #if _LIBCPP_STD_VER > 17
 template <class _Tp>
 struct unwrap_reference : __unwrap_reference<_Tp> { };
 
 template <class _Tp>
+using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
+
+template <class _Tp>
 struct unwrap_ref_decay : unwrap_reference<typename decay<_Tp>::type> { };
+
+template <class _Tp>
+using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
 #endif // > C++17
 
 template <class _Tp>
 struct __unwrap_ref_decay
 #if _LIBCPP_STD_VER > 17
     : unwrap_ref_decay<_Tp>
 #else
     : __unwrap_reference<typename decay<_Tp>::type>
 #endif
 { };
 
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
 #endif // _LIBCPP___FUNCTIONAL_UNWRAP_REF_H

libcxx/include/__functional/weak_result_type.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL_WEAK_RESULT_TYPE_H
+#define _LIBCPP___FUNCTIONAL_WEAK_RESULT_TYPE_H
+
+#include <__config>
+#include <__functional/binary_function.h>
+#include <__functional/unary_function.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+struct __has_result_type
+{
+private:
+    struct __two {char __lx; char __lxx;};
+    template <class _Up> static __two __test(...);
+    template <class _Up> static char __test(typename _Up::result_type* = 0);
+public:
+    static const bool value = sizeof(__test<_Tp>(0)) == 1;
+};
+
+// __weak_result_type
+
+template <class _Tp>
+struct __derives_from_unary_function
+{
+private:
+    struct __two {char __lx; char __lxx;};
+    static __two __test(...);
+    template <class _Ap, class _Rp>
+        static unary_function<_Ap, _Rp>
+        __test(const volatile unary_function<_Ap, _Rp>*);
+public:
+    static const bool value = !is_same<decltype(__test((_Tp*)0)), __two>::value;
+    typedef decltype(__test((_Tp*)0)) type;
+};
+
+template <class _Tp>
+struct __derives_from_binary_function
+{
+private:
+    struct __two {char __lx; char __lxx;};
+    static __two __test(...);
+    template <class _A1, class _A2, class _Rp>
+        static binary_function<_A1, _A2, _Rp>
+        __test(const volatile binary_function<_A1, _A2, _Rp>*);
+public:
+    static const bool value = !is_same<decltype(__test((_Tp*)0)), __two>::value;
+    typedef decltype(__test((_Tp*)0)) type;
+};
+
+template <class _Tp, bool = __derives_from_unary_function<_Tp>::value>
+struct __maybe_derive_from_unary_function  // bool is true
+    : public __derives_from_unary_function<_Tp>::type
+{
+};
+
+template <class _Tp>
+struct __maybe_derive_from_unary_function<_Tp, false>
+{
+};
+
+template <class _Tp, bool = __derives_from_binary_function<_Tp>::value>
+struct __maybe_derive_from_binary_function  // bool is true
+    : public __derives_from_binary_function<_Tp>::type
+{
+};
+
+template <class _Tp>
+struct __maybe_derive_from_binary_function<_Tp, false>
+{
+};
+
+template <class _Tp, bool = __has_result_type<_Tp>::value>
+struct __weak_result_type_imp // bool is true
+    : public __maybe_derive_from_unary_function<_Tp>,
+      public __maybe_derive_from_binary_function<_Tp>
+{
+    typedef _LIBCPP_NODEBUG_TYPE typename _Tp::result_type result_type;
+};
+
+template <class _Tp>
+struct __weak_result_type_imp<_Tp, false>
+    : public __maybe_derive_from_unary_function<_Tp>,
+      public __maybe_derive_from_binary_function<_Tp>
+{
+};
+
+template <class _Tp>
+struct __weak_result_type
+    : public __weak_result_type_imp<_Tp>
+{
+};
+
+// 0 argument case
+
+template <class _Rp>
+struct __weak_result_type<_Rp ()>
+{
+    typedef _LIBCPP_NODEBUG_TYPE  _Rp result_type;
+};
+
+template <class _Rp>
+struct __weak_result_type<_Rp (&)()>
+{
+    typedef _LIBCPP_NODEBUG_TYPE  _Rp result_type;
+};
+
+template <class _Rp>
+struct __weak_result_type<_Rp (*)()>
+{
+    typedef _LIBCPP_NODEBUG_TYPE  _Rp result_type;
+};
+
+// 1 argument case
+
+template <class _Rp, class _A1>
+struct __weak_result_type<_Rp (_A1)>
+    : public unary_function<_A1, _Rp>
+{
+};
+
+template <class _Rp, class _A1>
+struct __weak_result_type<_Rp (&)(_A1)>
+    : public unary_function<_A1, _Rp>
+{
+};
+
+template <class _Rp, class _A1>
+struct __weak_result_type<_Rp (*)(_A1)>
+    : public unary_function<_A1, _Rp>
+{
+};
+
+template <class _Rp, class _Cp>
+struct __weak_result_type<_Rp (_Cp::*)()>
+    : public unary_function<_Cp*, _Rp>
+{
+};
+
+template <class _Rp, class _Cp>
+struct __weak_result_type<_Rp (_Cp::*)() const>
+    : public unary_function<const _Cp*, _Rp>
+{
+};
+
+template <class _Rp, class _Cp>
+struct __weak_result_type<_Rp (_Cp::*)() volatile>
+    : public unary_function<volatile _Cp*, _Rp>
+{
+};
+
+template <class _Rp, class _Cp>
+struct __weak_result_type<_Rp (_Cp::*)() const volatile>
+    : public unary_function<const volatile _Cp*, _Rp>
+{
+};
+
+// 2 argument case
+
+template <class _Rp, class _A1, class _A2>
+struct __weak_result_type<_Rp (_A1, _A2)>
+    : public binary_function<_A1, _A2, _Rp>
+{
+};
+
+template <class _Rp, class _A1, class _A2>
+struct __weak_result_type<_Rp (*)(_A1, _A2)>
+    : public binary_function<_A1, _A2, _Rp>
+{
+};
+
+template <class _Rp, class _A1, class _A2>
+struct __weak_result_type<_Rp (&)(_A1, _A2)>
+    : public binary_function<_A1, _A2, _Rp>
+{
+};
+
+template <class _Rp, class _Cp, class _A1>
+struct __weak_result_type<_Rp (_Cp::*)(_A1)>
+    : public binary_function<_Cp*, _A1, _Rp>
+{
+};
+
+template <class _Rp, class _Cp, class _A1>
+struct __weak_result_type<_Rp (_Cp::*)(_A1) const>
+    : public binary_function<const _Cp*, _A1, _Rp>
+{
+};
+
+template <class _Rp, class _Cp, class _A1>
+struct __weak_result_type<_Rp (_Cp::*)(_A1) volatile>
+    : public binary_function<volatile _Cp*, _A1, _Rp>
+{
+};
+
+template <class _Rp, class _Cp, class _A1>
+struct __weak_result_type<_Rp (_Cp::*)(_A1) const volatile>
+    : public binary_function<const volatile _Cp*, _A1, _Rp>
+{
+};
+
+
+#ifndef _LIBCPP_CXX03_LANG
+// 3 or more arguments
+
+template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
+struct __weak_result_type<_Rp (_A1, _A2, _A3, _A4...)>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
+struct __weak_result_type<_Rp (&)(_A1, _A2, _A3, _A4...)>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
+struct __weak_result_type<_Rp (*)(_A1, _A2, _A3, _A4...)>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
+struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...)>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
+struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) const>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
+struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) volatile>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
+struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) const volatile>
+{
+    typedef _Rp result_type;
+};
+
+template <class _Tp, class ..._Args>
+struct __invoke_return
+{
+    typedef decltype(_VSTD::__invoke(declval<_Tp>(), declval<_Args>()...)) type;
+};
+
+#else // defined(_LIBCPP_CXX03_LANG)
+
+template <class _Ret, class _T1, bool _IsFunc, bool _IsBase>
+struct __enable_invoke_imp;
+
+template <class _Ret, class _T1>
+struct __enable_invoke_imp<_Ret, _T1, true, true> {
+    typedef _Ret _Bullet1;
+    typedef _Bullet1 type;
+};
+
+template <class _Ret, class _T1>
+struct __enable_invoke_imp<_Ret, _T1, true, false>  {
+    typedef _Ret _Bullet2;
+    typedef _Bullet2 type;
+};
+
+template <class _Ret, class _T1>
+struct __enable_invoke_imp<_Ret, _T1, false, true>  {
+    typedef typename add_lvalue_reference<
+                typename __apply_cv<_T1, _Ret>::type
+            >::type _Bullet3;
+    typedef _Bullet3 type;
+};
+
+template <class _Ret, class _T1>
+struct __enable_invoke_imp<_Ret, _T1, false, false>  {
+    typedef typename add_lvalue_reference<
+                typename __apply_cv<decltype(*declval<_T1>()), _Ret>::type
+            >::type _Bullet4;
+    typedef _Bullet4 type;
+};
+
+template <class _Ret, class _T1>
+struct __enable_invoke_imp<_Ret, _T1*, false, false>  {
+    typedef typename add_lvalue_reference<
+                typename __apply_cv<_T1, _Ret>::type
+            >::type _Bullet4;
+    typedef _Bullet4  type;
+};
+
+template <class _Fn, class _T1,
+          class _Traits = __member_pointer_traits<_Fn>,
+          class _Ret = typename _Traits::_ReturnType,
+          class _Class = typename _Traits::_ClassType>
+struct __enable_invoke : __enable_invoke_imp<
+    _Ret, _T1,
+    is_member_function_pointer<_Fn>::value,
+    is_base_of<_Class, typename remove_reference<_T1>::type>::value>
+{
+};
+
+__nat __invoke(__any, ...);
+
+// first bullet
+
+template <class _Fn, class _T1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet1
+__invoke(_Fn __f, _T1& __t1) {
+    return (__t1.*__f)();
+}
+
+template <class _Fn, class _T1, class _A0>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet1
+__invoke(_Fn __f, _T1& __t1, _A0& __a0) {
+    return (__t1.*__f)(__a0);
+}
+
+template <class _Fn, class _T1, class _A0, class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet1
+__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1) {
+    return (__t1.*__f)(__a0, __a1);
+}
+
+template <class _Fn, class _T1, class _A0, class _A1, class _A2>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet1
+__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2) {
+    return (__t1.*__f)(__a0, __a1, __a2);
+}
+
+template <class _Fn, class _T1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet2
+__invoke(_Fn __f, _T1& __t1) {
+    return ((*__t1).*__f)();
+}
+
+template <class _Fn, class _T1, class _A0>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet2
+__invoke(_Fn __f, _T1& __t1, _A0& __a0) {
+    return ((*__t1).*__f)(__a0);
+}
+
+template <class _Fn, class _T1, class _A0, class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet2
+__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1) {
+    return ((*__t1).*__f)(__a0, __a1);
+}
+
+template <class _Fn, class _T1, class _A0, class _A1, class _A2>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet2
+__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2) {
+    return ((*__t1).*__f)(__a0, __a1, __a2);
+}
+
+template <class _Fn, class _T1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet3
+__invoke(_Fn __f, _T1& __t1) {
+    return __t1.*__f;
+}
+
+template <class _Fn, class _T1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename __enable_invoke<_Fn, _T1>::_Bullet4
+__invoke(_Fn __f, _T1& __t1) {
+    return (*__t1).*__f;
+}
+
+// fifth bullet
+
+template <class _Fp>
+inline _LIBCPP_INLINE_VISIBILITY
+decltype(declval<_Fp&>()())
+__invoke(_Fp& __f)
+{
+    return __f();
+}
+
+template <class _Fp, class _A0>
+inline _LIBCPP_INLINE_VISIBILITY
+decltype(declval<_Fp&>()(declval<_A0&>()))
+__invoke(_Fp& __f, _A0& __a0)
+{
+    return __f(__a0);
+}
+
+template <class _Fp, class _A0, class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+decltype(declval<_Fp&>()(declval<_A0&>(), declval<_A1&>()))
+__invoke(_Fp& __f, _A0& __a0, _A1& __a1)
+{
+    return __f(__a0, __a1);
+}
+
+template <class _Fp, class _A0, class _A1, class _A2>
+inline _LIBCPP_INLINE_VISIBILITY
+decltype(declval<_Fp&>()(declval<_A0&>(), declval<_A1&>(), declval<_A2&>()))
+__invoke(_Fp& __f, _A0& __a0, _A1& __a1, _A2& __a2)
+{
+    return __f(__a0, __a1, __a2);
+}
+
+template <class _Fp, bool = __has_result_type<__weak_result_type<_Fp> >::value>
+struct __invoke_return
+{
+    typedef typename __weak_result_type<_Fp>::result_type type;
+};
+
+template <class _Fp>
+struct __invoke_return<_Fp, false>
+{
+    typedef decltype(_VSTD::__invoke(declval<_Fp&>())) type;
+};
+
+template <class _Tp, class _A0>
+struct __invoke_return0
+{
+    typedef decltype(_VSTD::__invoke(declval<_Tp&>(), declval<_A0&>())) type;
+};
+
+template <class _Rp, class _Tp, class _A0>
+struct __invoke_return0<_Rp _Tp::*, _A0>
+{
+    typedef typename __enable_invoke<_Rp _Tp::*, _A0>::type type;
+};
+
+template <class _Tp, class _A0, class _A1>
+struct __invoke_return1
+{
+    typedef decltype(_VSTD::__invoke(declval<_Tp&>(), declval<_A0&>(),
+                                                      declval<_A1&>())) type;
+};
+
+template <class _Rp, class _Class, class _A0, class _A1>
+struct __invoke_return1<_Rp _Class::*, _A0, _A1> {
+    typedef typename __enable_invoke<_Rp _Class::*, _A0>::type type;
+};
+
+template <class _Tp, class _A0, class _A1, class _A2>
+struct __invoke_return2
+{
+    typedef decltype(_VSTD::__invoke(declval<_Tp&>(), declval<_A0&>(),
+                                                      declval<_A1&>(),
+                                                      declval<_A2&>())) type;
+};
+
+template <class _Ret, class _Class, class _A0, class _A1, class _A2>
+struct __invoke_return2<_Ret _Class::*, _A0, _A1, _A2> {
+    typedef typename __enable_invoke<_Ret _Class::*, _A0>::type type;
+};
+
+#endif // !defined(_LIBCPP_CXX03_LANG)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL_WEAK_RESULT_TYPE_H

libcxx/include/__functional_base

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_FUNCTIONAL_BASE
 #define _LIBCPP_FUNCTIONAL_BASE
 
 #include <__config>
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/less.h>
+#include <__functional/reference_wrapper.h>
 #include <__functional/unary_function.h>
+#include <__functional/weak_result_type.h>
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
 #include <exception>
 #include <new>
 #include <type_traits>
 #include <typeinfo>
 #include <utility>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _Arg1, class _Arg2, class _Result>
-struct _LIBCPP_TEMPLATE_VIS binary_function
-{
-    typedef _Arg1   first_argument_type;
-    typedef _Arg2   second_argument_type;
-    typedef _Result result_type;
-};
-
-template <class _Tp>
-struct __has_result_type
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::result_type* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS less
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x < __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS less<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) < _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) < _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) < _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-// __weak_result_type
-
-template <class _Tp>
-struct __derives_from_unary_function
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    static __two __test(...);
-    template <class _Ap, class _Rp>
-        static unary_function<_Ap, _Rp>
-        __test(const volatile unary_function<_Ap, _Rp>*);
-public:
-    static const bool value = !is_same<decltype(__test((_Tp*)0)), __two>::value;
-    typedef decltype(__test((_Tp*)0)) type;
-};
-
-template <class _Tp>
-struct __derives_from_binary_function
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    static __two __test(...);
-    template <class _A1, class _A2, class _Rp>
-        static binary_function<_A1, _A2, _Rp>
-        __test(const volatile binary_function<_A1, _A2, _Rp>*);
-public:
-    static const bool value = !is_same<decltype(__test((_Tp*)0)), __two>::value;
-    typedef decltype(__test((_Tp*)0)) type;
-};
-
-template <class _Tp, bool = __derives_from_unary_function<_Tp>::value>
-struct __maybe_derive_from_unary_function  // bool is true
-    : public __derives_from_unary_function<_Tp>::type
-{
-};
-
-template <class _Tp>
-struct __maybe_derive_from_unary_function<_Tp, false>
-{
-};
-
-template <class _Tp, bool = __derives_from_binary_function<_Tp>::value>
-struct __maybe_derive_from_binary_function  // bool is true
-    : public __derives_from_binary_function<_Tp>::type
-{
-};
-
-template <class _Tp>
-struct __maybe_derive_from_binary_function<_Tp, false>
-{
-};
-
-template <class _Tp, bool = __has_result_type<_Tp>::value>
-struct __weak_result_type_imp // bool is true
-    : public __maybe_derive_from_unary_function<_Tp>,
-      public __maybe_derive_from_binary_function<_Tp>
-{
-    typedef _LIBCPP_NODEBUG_TYPE typename _Tp::result_type result_type;
-};
-
-template <class _Tp>
-struct __weak_result_type_imp<_Tp, false>
-    : public __maybe_derive_from_unary_function<_Tp>,
-      public __maybe_derive_from_binary_function<_Tp>
-{
-};
-
-template <class _Tp>
-struct __weak_result_type
-    : public __weak_result_type_imp<_Tp>
-{
-};
-
-// 0 argument case
-
-template <class _Rp>
-struct __weak_result_type<_Rp ()>
-{
-    typedef _LIBCPP_NODEBUG_TYPE  _Rp result_type;
-};
-
-template <class _Rp>
-struct __weak_result_type<_Rp (&)()>
-{
-    typedef _LIBCPP_NODEBUG_TYPE  _Rp result_type;
-};
-
-template <class _Rp>
-struct __weak_result_type<_Rp (*)()>
-{
-    typedef _LIBCPP_NODEBUG_TYPE  _Rp result_type;
-};
-
-// 1 argument case
-
-template <class _Rp, class _A1>
-struct __weak_result_type<_Rp (_A1)>
-    : public unary_function<_A1, _Rp>
-{
-};
-
-template <class _Rp, class _A1>
-struct __weak_result_type<_Rp (&)(_A1)>
-    : public unary_function<_A1, _Rp>
-{
-};
-
-template <class _Rp, class _A1>
-struct __weak_result_type<_Rp (*)(_A1)>
-    : public unary_function<_A1, _Rp>
-{
-};
-
-template <class _Rp, class _Cp>
-struct __weak_result_type<_Rp (_Cp::*)()>
-    : public unary_function<_Cp*, _Rp>
-{
-};
-
-template <class _Rp, class _Cp>
-struct __weak_result_type<_Rp (_Cp::*)() const>
-    : public unary_function<const _Cp*, _Rp>
-{
-};
-
-template <class _Rp, class _Cp>
-struct __weak_result_type<_Rp (_Cp::*)() volatile>
-    : public unary_function<volatile _Cp*, _Rp>
-{
-};
-
-template <class _Rp, class _Cp>
-struct __weak_result_type<_Rp (_Cp::*)() const volatile>
-    : public unary_function<const volatile _Cp*, _Rp>
-{
-};
-
-// 2 argument case
-
-template <class _Rp, class _A1, class _A2>
-struct __weak_result_type<_Rp (_A1, _A2)>
-    : public binary_function<_A1, _A2, _Rp>
-{
-};
-
-template <class _Rp, class _A1, class _A2>
-struct __weak_result_type<_Rp (*)(_A1, _A2)>
-    : public binary_function<_A1, _A2, _Rp>
-{
-};
-
-template <class _Rp, class _A1, class _A2>
-struct __weak_result_type<_Rp (&)(_A1, _A2)>
-    : public binary_function<_A1, _A2, _Rp>
-{
-};
-
-template <class _Rp, class _Cp, class _A1>
-struct __weak_result_type<_Rp (_Cp::*)(_A1)>
-    : public binary_function<_Cp*, _A1, _Rp>
-{
-};
-
-template <class _Rp, class _Cp, class _A1>
-struct __weak_result_type<_Rp (_Cp::*)(_A1) const>
-    : public binary_function<const _Cp*, _A1, _Rp>
-{
-};
-
-template <class _Rp, class _Cp, class _A1>
-struct __weak_result_type<_Rp (_Cp::*)(_A1) volatile>
-    : public binary_function<volatile _Cp*, _A1, _Rp>
-{
-};
-
-template <class _Rp, class _Cp, class _A1>
-struct __weak_result_type<_Rp (_Cp::*)(_A1) const volatile>
-    : public binary_function<const volatile _Cp*, _A1, _Rp>
-{
-};
-
-
-#ifndef _LIBCPP_CXX03_LANG
-// 3 or more arguments
-
-template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
-struct __weak_result_type<_Rp (_A1, _A2, _A3, _A4...)>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
-struct __weak_result_type<_Rp (&)(_A1, _A2, _A3, _A4...)>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
-struct __weak_result_type<_Rp (*)(_A1, _A2, _A3, _A4...)>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
-struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...)>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
-struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) const>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
-struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) volatile>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Rp, class _Cp, class _A1, class _A2, class ..._A3>
-struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) const volatile>
-{
-    typedef _Rp result_type;
-};
-
-template <class _Tp, class ..._Args>
-struct __invoke_return
-{
-    typedef decltype(_VSTD::__invoke(declval<_Tp>(), declval<_Args>()...)) type;
-};
-
-#else // defined(_LIBCPP_CXX03_LANG)
-
-#include <__functional_base_03>
-
-#endif // !defined(_LIBCPP_CXX03_LANG)
-
-
-template <class _Ret, bool = is_void<_Ret>::value>
-struct __invoke_void_return_wrapper
-{
-#ifndef _LIBCPP_CXX03_LANG
-    template <class ..._Args>
-    static _Ret __call(_Args&&... __args) {
-        return _VSTD::__invoke(_VSTD::forward<_Args>(__args)...);
-    }
-#else
-    template <class _Fn>
-    static _Ret __call(_Fn __f) {
-        return _VSTD::__invoke(__f);
-    }
-
-    template <class _Fn, class _A0>
-    static _Ret __call(_Fn __f, _A0& __a0) {
-        return _VSTD::__invoke(__f, __a0);
-    }
-
-    template <class _Fn, class _A0, class _A1>
-    static _Ret __call(_Fn __f, _A0& __a0, _A1& __a1) {
-        return _VSTD::__invoke(__f, __a0, __a1);
-    }
-
-    template <class _Fn, class _A0, class _A1, class _A2>
-    static _Ret __call(_Fn __f, _A0& __a0, _A1& __a1, _A2& __a2){
-        return _VSTD::__invoke(__f, __a0, __a1, __a2);
-    }
-#endif
-};
-
-template <class _Ret>
-struct __invoke_void_return_wrapper<_Ret, true>
-{
-#ifndef _LIBCPP_CXX03_LANG
-    template <class ..._Args>
-    static void __call(_Args&&... __args) {
-        _VSTD::__invoke(_VSTD::forward<_Args>(__args)...);
-    }
-#else
-    template <class _Fn>
-    static void __call(_Fn __f) {
-        _VSTD::__invoke(__f);
-    }
-
-    template <class _Fn, class _A0>
-    static void __call(_Fn __f, _A0& __a0) {
-        _VSTD::__invoke(__f, __a0);
-    }
-
-    template <class _Fn, class _A0, class _A1>
-    static void __call(_Fn __f, _A0& __a0, _A1& __a1) {
-        _VSTD::__invoke(__f, __a0, __a1);
-    }
-
-    template <class _Fn, class _A0, class _A1, class _A2>
-    static void __call(_Fn __f, _A0& __a0, _A1& __a1, _A2& __a2) {
-        _VSTD::__invoke(__f, __a0, __a1, __a2);
-    }
-#endif
-};
-
-template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS reference_wrapper
-#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : public __weak_result_type<_Tp>
-#endif
-{
-public:
-    // types
-    typedef _Tp type;
-private:
-    type* __f_;
-
-#ifndef _LIBCPP_CXX03_LANG
-    static void __fun(_Tp&) _NOEXCEPT;
-    static void __fun(_Tp&&) = delete;
-#endif
-
-public:
-    // construct/copy/destroy
-#ifdef _LIBCPP_CXX03_LANG
-    _LIBCPP_INLINE_VISIBILITY
-    reference_wrapper(type& __f) _NOEXCEPT
-        : __f_(_VSTD::addressof(__f)) {}
-#else
-    template <class _Up, class = _EnableIf<!__is_same_uncvref<_Up, reference_wrapper>::value, decltype(__fun(declval<_Up>())) >>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    reference_wrapper(_Up&& __u) _NOEXCEPT_(noexcept(__fun(declval<_Up>()))) {
-        type& __f = static_cast<_Up&&>(__u);
-        __f_ = _VSTD::addressof(__f);
-    }
-#endif
-
-    // access
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    operator type&() const _NOEXCEPT {return *__f_;}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    type& get() const _NOEXCEPT {return *__f_;}
-
-#ifndef _LIBCPP_CXX03_LANG
-    // invoke
-    template <class... _ArgTypes>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    typename __invoke_of<type&, _ArgTypes...>::type
-    operator() (_ArgTypes&&... __args) const {
-        return _VSTD::__invoke(get(), _VSTD::forward<_ArgTypes>(__args)...);
-    }
-#else
-
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return<type>::type
-    operator() () const {
-        return _VSTD::__invoke(get());
-    }
-
-    template <class _A0>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return0<type, _A0>::type
-    operator() (_A0& __a0) const {
-        return _VSTD::__invoke(get(), __a0);
-    }
-
-    template <class _A0>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return0<type, _A0 const>::type
-    operator() (_A0 const& __a0) const {
-        return _VSTD::__invoke(get(), __a0);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0, _A1>::type
-    operator() (_A0& __a0, _A1& __a1) const {
-        return _VSTD::__invoke(get(), __a0, __a1);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0 const, _A1>::type
-    operator() (_A0 const& __a0, _A1& __a1) const {
-        return _VSTD::__invoke(get(), __a0, __a1);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0, _A1 const>::type
-    operator() (_A0& __a0, _A1 const& __a1) const {
-        return _VSTD::__invoke(get(), __a0, __a1);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0 const, _A1 const>::type
-    operator() (_A0 const& __a0, _A1 const& __a1) const {
-        return _VSTD::__invoke(get(), __a0, __a1);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1, _A2>::type
-    operator() (_A0& __a0, _A1& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1, _A2>::type
-    operator() (_A0 const& __a0, _A1& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1 const, _A2>::type
-    operator() (_A0& __a0, _A1 const& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1, _A2 const>::type
-    operator() (_A0& __a0, _A1& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1 const, _A2>::type
-    operator() (_A0 const& __a0, _A1 const& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1, _A2 const>::type
-    operator() (_A0 const& __a0, _A1& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1 const, _A2 const>::type
-    operator() (_A0& __a0, _A1 const& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1 const, _A2 const>::type
-    operator() (_A0 const& __a0, _A1 const& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(get(), __a0, __a1, __a2);
-    }
-#endif // _LIBCPP_CXX03_LANG
-};
-
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
-template <class _Tp>
-reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
-#endif
-
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-reference_wrapper<_Tp>
-ref(_Tp& __t) _NOEXCEPT
-{
-    return reference_wrapper<_Tp>(__t);
-}
-
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-reference_wrapper<_Tp>
-ref(reference_wrapper<_Tp> __t) _NOEXCEPT
-{
-    return _VSTD::ref(__t.get());
-}
-
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-reference_wrapper<const _Tp>
-cref(const _Tp& __t) _NOEXCEPT
-{
-    return reference_wrapper<const _Tp>(__t);
-}
-
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-reference_wrapper<const _Tp>
-cref(reference_wrapper<_Tp> __t) _NOEXCEPT
-{
-    return _VSTD::cref(__t.get());
-}
-
-#ifndef _LIBCPP_CXX03_LANG
-template <class _Tp> void ref(const _Tp&&) = delete;
-template <class _Tp> void cref(const _Tp&&) = delete;
-#endif
-
-#if _LIBCPP_STD_VER > 11
-template <class _Tp, class, class = void>
-struct __is_transparent : false_type {};
-
-template <class _Tp, class _Up>
-struct __is_transparent<_Tp, _Up,
-                        typename __void_t<typename _Tp::is_transparent>::type>
-   : true_type {};
-#endif
-
-// allocator_arg_t
-
-struct _LIBCPP_TEMPLATE_VIS allocator_arg_t { explicit allocator_arg_t() = default; };
-
-#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
-extern _LIBCPP_EXPORTED_FROM_ABI const allocator_arg_t allocator_arg;
-#else
-/* _LIBCPP_INLINE_VAR */ constexpr allocator_arg_t allocator_arg = allocator_arg_t();
-#endif
-
-// uses_allocator
-
-template <class _Tp>
-struct __has_allocator_type
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::allocator_type* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
-
-template <class _Tp, class _Alloc, bool = __has_allocator_type<_Tp>::value>
-struct __uses_allocator
-    : public integral_constant<bool,
-        is_convertible<_Alloc, typename _Tp::allocator_type>::value>
-{
-};
-
-template <class _Tp, class _Alloc>
-struct __uses_allocator<_Tp, _Alloc, false>
-    : public false_type
-{
-};
-
-template <class _Tp, class _Alloc>
-struct _LIBCPP_TEMPLATE_VIS uses_allocator
-    : public __uses_allocator<_Tp, _Alloc>
-{
-};
-
-#if _LIBCPP_STD_VER > 14
-template <class _Tp, class _Alloc>
-_LIBCPP_INLINE_VAR constexpr size_t uses_allocator_v = uses_allocator<_Tp, _Alloc>::value;
-#endif
-
-#ifndef _LIBCPP_CXX03_LANG
-
-// allocator construction
-
-template <class _Tp, class _Alloc, class ..._Args>
-struct __uses_alloc_ctor_imp
-{
-    typedef _LIBCPP_NODEBUG_TYPE typename __uncvref<_Alloc>::type _RawAlloc;
-    static const bool __ua = uses_allocator<_Tp, _RawAlloc>::value;
-    static const bool __ic =
-        is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value;
-    static const int value = __ua ? 2 - __ic : 0;
-};
-
-template <class _Tp, class _Alloc, class ..._Args>
-struct __uses_alloc_ctor
-    : integral_constant<int, __uses_alloc_ctor_imp<_Tp, _Alloc, _Args...>::value>
-    {};
-
-template <class _Tp, class _Allocator, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-void __user_alloc_construct_impl (integral_constant<int, 0>, _Tp *__storage, const _Allocator &, _Args &&... __args )
-{
-    new (__storage) _Tp (_VSTD::forward<_Args>(__args)...);
-}
-
-// FIXME: This should have a version which takes a non-const alloc.
-template <class _Tp, class _Allocator, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-void __user_alloc_construct_impl (integral_constant<int, 1>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
-{
-    new (__storage) _Tp (allocator_arg, __a, _VSTD::forward<_Args>(__args)...);
-}
-
-// FIXME: This should have a version which takes a non-const alloc.
-template <class _Tp, class _Allocator, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-void __user_alloc_construct_impl (integral_constant<int, 2>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
-{
-    new (__storage) _Tp (_VSTD::forward<_Args>(__args)..., __a);
-}
-
-#endif // _LIBCPP_CXX03_LANG
-
-#if _LIBCPP_STD_VER > 14
-
-template <class _Fn, class ..._Args>
-_LIBCPP_CONSTEXPR_AFTER_CXX17 invoke_result_t<_Fn, _Args...>
-invoke(_Fn&& __f, _Args&&... __args)
-    noexcept(is_nothrow_invocable_v<_Fn, _Args...>)
-{
-    return _VSTD::__invoke(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)...);
-}
-
-#endif // _LIBCPP_STD_VER > 14
-
-_LIBCPP_END_NAMESPACE_STD
-
 #endif // _LIBCPP_FUNCTIONAL_BASE

libcxx/include/__functional_base_03

-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP_FUNCTIONAL_BASE_03
-#define _LIBCPP_FUNCTIONAL_BASE_03
-
-// manual variadic expansion for <functional>
-
-// __invoke
-
-template <class _Ret, class _T1, bool _IsFunc, bool _IsBase>
-struct __enable_invoke_imp;
-
-template <class _Ret, class _T1>
-struct __enable_invoke_imp<_Ret, _T1, true, true> {
-    typedef _Ret _Bullet1;
-    typedef _Bullet1 type;
-};
-
-template <class _Ret, class _T1>
-struct __enable_invoke_imp<_Ret, _T1, true, false>  {
-    typedef _Ret _Bullet2;
-    typedef _Bullet2 type;
-};
-
-template <class _Ret, class _T1>
-struct __enable_invoke_imp<_Ret, _T1, false, true>  {
-    typedef typename add_lvalue_reference<
-                typename __apply_cv<_T1, _Ret>::type
-            >::type _Bullet3;
-    typedef _Bullet3 type;
-};
-
-template <class _Ret, class _T1>
-struct __enable_invoke_imp<_Ret, _T1, false, false>  {
-    typedef typename add_lvalue_reference<
-                typename __apply_cv<decltype(*declval<_T1>()), _Ret>::type
-            >::type _Bullet4;
-    typedef _Bullet4 type;
-};
-
-template <class _Ret, class _T1>
-struct __enable_invoke_imp<_Ret, _T1*, false, false>  {
-    typedef typename add_lvalue_reference<
-                typename __apply_cv<_T1, _Ret>::type
-            >::type _Bullet4;
-    typedef _Bullet4  type;
-};
-
-template <class _Fn, class _T1,
-          class _Traits = __member_pointer_traits<_Fn>,
-          class _Ret = typename _Traits::_ReturnType,
-          class _Class = typename _Traits::_ClassType>
-struct __enable_invoke : __enable_invoke_imp<
-    _Ret, _T1,
-    is_member_function_pointer<_Fn>::value,
-    is_base_of<_Class, typename remove_reference<_T1>::type>::value>
-{
-};
-
-__nat __invoke(__any, ...);
-
-// first bullet
-
-template <class _Fn, class _T1>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet1
-__invoke(_Fn __f, _T1& __t1) {
-    return (__t1.*__f)();
-}
-
-template <class _Fn, class _T1, class _A0>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet1
-__invoke(_Fn __f, _T1& __t1, _A0& __a0) {
-    return (__t1.*__f)(__a0);
-}
-
-template <class _Fn, class _T1, class _A0, class _A1>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet1
-__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1) {
-    return (__t1.*__f)(__a0, __a1);
-}
-
-template <class _Fn, class _T1, class _A0, class _A1, class _A2>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet1
-__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2) {
-    return (__t1.*__f)(__a0, __a1, __a2);
-}
-
-template <class _Fn, class _T1>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet2
-__invoke(_Fn __f, _T1& __t1) {
-    return ((*__t1).*__f)();
-}
-
-template <class _Fn, class _T1, class _A0>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet2
-__invoke(_Fn __f, _T1& __t1, _A0& __a0) {
-    return ((*__t1).*__f)(__a0);
-}
-
-template <class _Fn, class _T1, class _A0, class _A1>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet2
-__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1) {
-    return ((*__t1).*__f)(__a0, __a1);
-}
-
-template <class _Fn, class _T1, class _A0, class _A1, class _A2>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet2
-__invoke(_Fn __f, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2) {
-    return ((*__t1).*__f)(__a0, __a1, __a2);
-}
-
-template <class _Fn, class _T1>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet3
-__invoke(_Fn __f, _T1& __t1) {
-    return __t1.*__f;
-}
-
-template <class _Fn, class _T1>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __enable_invoke<_Fn, _T1>::_Bullet4
-__invoke(_Fn __f, _T1& __t1) {
-    return (*__t1).*__f;
-}
-
-// fifth bullet
-
-template <class _Fp>
-inline _LIBCPP_INLINE_VISIBILITY
-decltype(declval<_Fp&>()())
-__invoke(_Fp& __f)
-{
-    return __f();
-}
-
-template <class _Fp, class _A0>
-inline _LIBCPP_INLINE_VISIBILITY
-decltype(declval<_Fp&>()(declval<_A0&>()))
-__invoke(_Fp& __f, _A0& __a0)
-{
-    return __f(__a0);
-}
-
-template <class _Fp, class _A0, class _A1>
-inline _LIBCPP_INLINE_VISIBILITY
-decltype(declval<_Fp&>()(declval<_A0&>(), declval<_A1&>()))
-__invoke(_Fp& __f, _A0& __a0, _A1& __a1)
-{
-    return __f(__a0, __a1);
-}
-
-template <class _Fp, class _A0, class _A1, class _A2>
-inline _LIBCPP_INLINE_VISIBILITY
-decltype(declval<_Fp&>()(declval<_A0&>(), declval<_A1&>(), declval<_A2&>()))
-__invoke(_Fp& __f, _A0& __a0, _A1& __a1, _A2& __a2)
-{
-    return __f(__a0, __a1, __a2);
-}
-
-template <class _Fp, bool = __has_result_type<__weak_result_type<_Fp> >::value>
-struct __invoke_return
-{
-    typedef typename __weak_result_type<_Fp>::result_type type;
-};
-
-template <class _Fp>
-struct __invoke_return<_Fp, false>
-{
-    typedef decltype(_VSTD::__invoke(declval<_Fp&>())) type;
-};
-
-template <class _Tp, class _A0>
-struct __invoke_return0
-{
-    typedef decltype(_VSTD::__invoke(declval<_Tp&>(), declval<_A0&>())) type;
-};
-
-template <class _Rp, class _Tp, class _A0>
-struct __invoke_return0<_Rp _Tp::*, _A0>
-{
-    typedef typename __enable_invoke<_Rp _Tp::*, _A0>::type type;
-};
-
-template <class _Tp, class _A0, class _A1>
-struct __invoke_return1
-{
-    typedef decltype(_VSTD::__invoke(declval<_Tp&>(), declval<_A0&>(),
-                                                      declval<_A1&>())) type;
-};
-
-template <class _Rp, class _Class, class _A0, class _A1>
-struct __invoke_return1<_Rp _Class::*, _A0, _A1> {
-    typedef typename __enable_invoke<_Rp _Class::*, _A0>::type type;
-};
-
-template <class _Tp, class _A0, class _A1, class _A2>
-struct __invoke_return2
-{
-    typedef decltype(_VSTD::__invoke(declval<_Tp&>(), declval<_A0&>(),
-                                                      declval<_A1&>(),
-                                                      declval<_A2&>())) type;
-};
-
-template <class _Ret, class _Class, class _A0, class _A1, class _A2>
-struct __invoke_return2<_Ret _Class::*, _A0, _A1, _A2> {
-    typedef typename __enable_invoke<_Ret _Class::*, _A0>::type type;
-};
-#endif // _LIBCPP_FUNCTIONAL_BASE_03

libcxx/include/__iterator/advance.h

 #define _LIBCPP___ITERATOR_ADVANCE_H
 
 #include <__config>
 #include <__debug>
 #include <__function_like.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
 #include <__iterator/iterator_traits.h>
+#include <cstdlib>
 #include <concepts>
 #include <limits>
 #include <type_traits>
 #include <utility>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif

libcxx/include/__memory/allocator_arg_t.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FUNCTIONAL___ALLOCATOR_ARG_T_H
+#define _LIBCPP___FUNCTIONAL___ALLOCATOR_ARG_T_H
+
+#include <__config>
+#include <__memory/uses_allocator.h>
+#include <__utility/forward.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct _LIBCPP_TEMPLATE_VIS allocator_arg_t { explicit allocator_arg_t() = default; };
+
+#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
+extern _LIBCPP_EXPORTED_FROM_ABI const allocator_arg_t allocator_arg;
+#else
+/* _LIBCPP_INLINE_VAR */ constexpr allocator_arg_t allocator_arg = allocator_arg_t();
+#endif
+
+#ifndef _LIBCPP_CXX03_LANG
+
+// allocator construction
+
+template <class _Tp, class _Alloc, class ..._Args>
+struct __uses_alloc_ctor_imp
+{
+    typedef _LIBCPP_NODEBUG_TYPE typename __uncvref<_Alloc>::type _RawAlloc;
+    static const bool __ua = uses_allocator<_Tp, _RawAlloc>::value;
+    static const bool __ic =
+        is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value;
+    static const int value = __ua ? 2 - __ic : 0;
+};
+
+template <class _Tp, class _Alloc, class ..._Args>
+struct __uses_alloc_ctor
+    : integral_constant<int, __uses_alloc_ctor_imp<_Tp, _Alloc, _Args...>::value>
+    {};
+
+template <class _Tp, class _Allocator, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+void __user_alloc_construct_impl (integral_constant<int, 0>, _Tp *__storage, const _Allocator &, _Args &&... __args )
+{
+    new (__storage) _Tp (_VSTD::forward<_Args>(__args)...);
+}
+
+// FIXME: This should have a version which takes a non-const alloc.
+template <class _Tp, class _Allocator, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+void __user_alloc_construct_impl (integral_constant<int, 1>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
+{
+    new (__storage) _Tp (allocator_arg, __a, _VSTD::forward<_Args>(__args)...);
+}
+
+// FIXME: This should have a version which takes a non-const alloc.
+template <class _Tp, class _Allocator, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+void __user_alloc_construct_impl (integral_constant<int, 2>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
+{
+    new (__storage) _Tp (_VSTD::forward<_Args>(__args)..., __a);
+}
+
+#endif // _LIBCPP_CXX03_LANG
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FUNCTIONAL___ALLOCATOR_ARG_T_H

libcxx/include/__memory/shared_ptr.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___MEMORY_SHARED_PTR_H
 #define _LIBCPP___MEMORY_SHARED_PTR_H
 
 #include <__availability>
 #include <__config>
-#include <__functional_base> // std::less, std::binary_function
+#include <__functional/binary_function.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/less.h>
+#include <__functional_base>
 #include <__memory/addressof.h>
 #include <__memory/allocation_guard.h>
 #include <__memory/allocator.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/compressed_pair.h>
 #include <__memory/pointer_traits.h>
 #include <__memory/unique_ptr.h>
 #include <__utility/forward.h>
 #include <cstddef>
 #include <cstdlib> // abort
 #include <iosfwd>
 #include <stdexcept>
+#include <typeinfo>
 #include <type_traits>
 #include <utility>
 #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 #  include <atomic>
 #endif
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 #   include <__memory/auto_ptr.h>

libcxx/include/__memory/unique_ptr.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___MEMORY_UNIQUE_PTR_H
 #define _LIBCPP___MEMORY_UNIQUE_PTR_H
 
 #include <__config>
-#include <__functional_base> // std::less
 #include <__functional/hash.h>
+#include <__functional/less.h>
+#include <__functional_base>
 #include <__memory/allocator_traits.h> // __pointer
 #include <__memory/compressed_pair.h>
 #include <__utility/forward.h>
 #include <cstddef>
 #include <type_traits>
 #include <utility>
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)

libcxx/include/__memory/uses_allocator.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MEMORY_USES_ALLOCATOR_H
+#define _LIBCPP___MEMORY_USES_ALLOCATOR_H
+
+#include <__config>
+#include <cstddef>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+struct __has_allocator_type
+{
+private:
+    struct __two {char __lx; char __lxx;};
+    template <class _Up> static __two __test(...);
+    template <class _Up> static char __test(typename _Up::allocator_type* = 0);
+public:
+    static const bool value = sizeof(__test<_Tp>(0)) == 1;
+};
+
+template <class _Tp, class _Alloc, bool = __has_allocator_type<_Tp>::value>
+struct __uses_allocator
+    : public integral_constant<bool,
+        is_convertible<_Alloc, typename _Tp::allocator_type>::value>
+{
+};
+
+template <class _Tp, class _Alloc>
+struct __uses_allocator<_Tp, _Alloc, false>
+    : public false_type
+{
+};
+
+template <class _Tp, class _Alloc>
+struct _LIBCPP_TEMPLATE_VIS uses_allocator
+    : public __uses_allocator<_Tp, _Alloc>
+{
+};
+
+#if _LIBCPP_STD_VER > 14
+template <class _Tp, class _Alloc>
+_LIBCPP_INLINE_VAR constexpr size_t uses_allocator_v = uses_allocator<_Tp, _Alloc>::value;
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___MEMORY_USES_ALLOCATOR_H

libcxx/include/__ranges/ref_view.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 #ifndef _LIBCPP___RANGES_REF_VIEW_H
 #define _LIBCPP___RANGES_REF_VIEW_H
 
 #include <__config>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
 #include <__iterator/iterator_traits.h>
+#include <__memory/addressof.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
 #include <__ranges/data.h>
 #include <__ranges/empty.h>
 #include <__ranges/size.h>
 #include <__ranges/view_interface.h>
 #include <concepts>
 #include <type_traits>

libcxx/include/__string

 // -*- C++ -*-
 //===-------------------------- __string ----------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___STRING
 #define _LIBCPP___STRING
 
 #include <__config>
-#include <algorithm>  // for search and min
-#include <cstdio>     // for EOF
-#include <cstring>    // for memcpy
-#include <cwchar>     // for wmemcpy
-#include <memory>     // for __murmur2_or_cityhash
+#include <__algorithm/copy.h>
+#include <__algorithm/copy_backward.h>
+#include <__algorithm/copy_n.h>
+#include <__algorithm/fill_n.h>
+#include <__algorithm/find_first_of.h>
+#include <__algorithm/find_end.h>
+#include <__algorithm/min.h>
+#include <__functional/hash.h>     // for __murmur2_or_cityhash
+#include <__iterator/iterator_traits.h>
+#include <cstdio>      // for EOF
+#include <cstdint>     // for uint_least16_t
+#include <cstring>     // for memcpy
+#include <cwchar>      // for wmemcpy
+#include <type_traits> // for __libcpp_is_constant_evaluated
 
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS

libcxx/include/concepts

namespace std {
   // [concept.strictweakorder], concept strict_weak_order
   template<class R, class T, class U>
     concept strict_weak_order = see below;
 }
 
 */
 
 #include <__config>
+#include <__functional/invoke.h>
 #include <__functional_base>
 #include <type_traits>
 #include <utility>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif

libcxx/include/experimental/__memory

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_EXPERIMENTAL___MEMORY
 #define _LIBCPP_EXPERIMENTAL___MEMORY
 
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
 #include <experimental/__config>
 #include <experimental/utility> // for erased_type
 #include <__functional_base>
 #include <type_traits>
 
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
 template <
struct __lfts_uses_alloc_ctor
   : integral_constant<int,
         __lfts_uses_alloc_ctor_imp<
             __lfts_uses_allocator<_Tp, _Alloc>::value
           , _Tp, _Alloc, _Args...
         >::value
     >
 {};
 
+template <class _Tp, class _Allocator, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+void __user_alloc_construct_impl (integral_constant<int, 0>, _Tp *__storage, const _Allocator &, _Args &&... __args )
+{
+    new (__storage) _Tp (_VSTD::forward<_Args>(__args)...);
+}
+
+// FIXME: This should have a version which takes a non-const alloc.
+template <class _Tp, class _Allocator, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+void __user_alloc_construct_impl (integral_constant<int, 1>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
+{
+    new (__storage) _Tp (allocator_arg, __a, _VSTD::forward<_Args>(__args)...);
+}
+
+// FIXME: This should have a version which takes a non-const alloc.
+template <class _Tp, class _Allocator, class... _Args>
+inline _LIBCPP_INLINE_VISIBILITY
+void __user_alloc_construct_impl (integral_constant<int, 2>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
+{
+    new (__storage) _Tp (_VSTD::forward<_Args>(__args)..., __a);
+}
+
 template <class _Tp, class _Alloc, class ..._Args>
 inline _LIBCPP_INLINE_VISIBILITY
 void __lfts_user_alloc_construct(
     _Tp * __store, const _Alloc & __a, _Args &&... __args)
 {
-    _VSTD::__user_alloc_construct_impl(
+    ::std::experimental::fundamentals_v1::__user_alloc_construct_impl(
         typename __lfts_uses_alloc_ctor<_Tp, _Alloc, _Args...>::type()
        , __store, __a, _VSTD::forward<_Args>(__args)...
        );
 }
 
 _LIBCPP_END_NAMESPACE_LFTS
 
 #endif /* _LIBCPP_EXPERIMENTAL___MEMORY */

libcxx/include/experimental/functional

inline namespace fundamentals_v1 {
 
   template<class R, class... ArgTypes, class Alloc>
   struct uses_allocator<experimental::function<R(ArgTypes...)>, Alloc>;
 
 } // namespace std
 
 */
 
+#include <__memory/uses_allocator.h>
 #include <experimental/__config>
 #include <functional>
 #include <algorithm>
 #include <type_traits>
 #include <vector>
 #include <array>
 #include <unordered_map>
 

libcxx/include/ext/__hash

 // -*- C++ -*-
 //===------------------------- hash_set ------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_EXT_HASH
 #define _LIBCPP_EXT_HASH
 
 #pragma GCC system_header
 
+#include <__string>
 #include <string>
 #include <cstring>
 
 namespace __gnu_cxx {
 
 template <typename _Tp> struct _LIBCPP_TEMPLATE_VIS hash { };
 
 template <> struct _LIBCPP_TEMPLATE_VIS hash<const char*>

libcxx/include/functional

 // -*- C++ -*-
-//===------------------------ functional ----------------------------------===//
+//===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_FUNCTIONAL
POLICY:  For non-variadic implementations, the number of arguments is limited
          to 3.  It is hoped that the need for non-variadic implementations
          will be minimal.
 
 */
 
 #include <__algorithm/search.h>
 #include <__config>
 #include <__debug>
-#include <__functional_base>
+#include <__functional/binary_function.h> // TODO: deprecate
+#include <__functional/bind_front.h>
+#include <__functional/bind.h>
+#include <__functional/bit_and.h>
+#include <__functional/bit_not.h>
+#include <__functional/bit_or.h>
+#include <__functional/bit_xor.h>
+#include <__functional/default_searcher.h>
+#include <__functional//binary_negate.h>
+#include <__functional//binder1st.h>
+#include <__functional//binder2nd.h>
+#include <__functional//mem_fun_ref.h>
+#include <__functional//pointer_to_binary_function.h>
+#include <__functional//pointer_to_unary_function.h>
+#include <__functional//unary_negate.h>
+#include <__functional/divides.h>
+#include <__functional/equal_to.h>
+#include <__functional/function.h>
+#include <__functional/greater_equal.h>
+#include <__functional/greater.h>
 #include <__functional/hash.h>
-#include <__functional/unary_function.h>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
+#include <__functional/less_equal.h>
+#include <__functional/less.h>
+#include <__functional/logical_and.h>
+#include <__functional/logical_not.h>
+#include <__functional/logical_or.h>
+#include <__functional/mem_fn.h> // TODO: deprecate
+#include <__functional/minus.h>
+#include <__functional/modulus.h>
+#include <__functional/multiplies.h>
+#include <__functional/negate.h>
+#include <__functional/not_equal_to.h>
+#include <__functional/not_fn.h>
+#include <__functional/plus.h>
+#include <__functional/ranges/equal_to.h>
+#include <__functional/ranges/greater_equal.h>
+#include <__functional/ranges/greater.h>
+#include <__functional/ranges/less_equal.h>
+#include <__functional/ranges/less.h>
+#include <__functional/ranges/not_equal_to.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/unary_function.h> // TODO: deprecate
 #include <__functional/unwrap_ref.h>
 #include <__utility/forward.h>
 #include <concepts>
 #include <exception>
 #include <memory>
 #include <tuple>
 #include <type_traits>
 #include <typeinfo>
 #include <utility>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS plus
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x + __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS plus<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS minus
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x - __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS minus<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) - _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) - _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) - _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS multiplies
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x * __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS multiplies<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) * _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) * _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) * _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS divides
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x / __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS divides<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) / _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) / _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) / _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS modulus
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x % __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS modulus<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) % _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) % _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) % _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS negate
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : unary_function<_Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x) const
-        {return -__x;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS negate<void>
-{
-    template <class _Tp>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_Tp&& __x) const
-    _NOEXCEPT_(noexcept(- _VSTD::forward<_Tp>(__x)))
-    -> decltype        (- _VSTD::forward<_Tp>(__x))
-        { return        - _VSTD::forward<_Tp>(__x); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS equal_to
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x == __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS equal_to<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) == _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) == _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) == _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS not_equal_to
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x != __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS not_equal_to<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) != _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) != _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) != _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS greater
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x > __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS greater<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) > _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) > _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) > _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-// less in <__functional_base>
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS greater_equal
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x >= __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS greater_equal<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) >= _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) >= _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) >= _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS less_equal
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x <= __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS less_equal<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) <= _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) <= _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) <= _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS logical_and
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x && __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS logical_and<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) && _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) && _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) && _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS logical_or
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x || __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS logical_or<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) || _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) || _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) || _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS logical_not
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : unary_function<_Tp, bool>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef bool __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef bool result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _Tp& __x) const
-        {return !__x;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS logical_not<void>
-{
-    template <class _Tp>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_Tp&& __x) const
-    _NOEXCEPT_(noexcept(!_VSTD::forward<_Tp>(__x)))
-    -> decltype        (!_VSTD::forward<_Tp>(__x))
-        { return        !_VSTD::forward<_Tp>(__x); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS bit_and
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x & __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS bit_and<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) & _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) & _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) & _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS bit_or
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x | __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS bit_or<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) | _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) | _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) | _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-#if _LIBCPP_STD_VER > 11
-template <class _Tp = void>
-#else
-template <class _Tp>
-#endif
-struct _LIBCPP_TEMPLATE_VIS bit_xor
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : binary_function<_Tp, _Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-    typedef _Tp __result_type;  // used by valarray
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp first_argument_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp second_argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x, const _Tp& __y) const
-        {return __x ^ __y;}
-};
-
-#if _LIBCPP_STD_VER > 11
-template <>
-struct _LIBCPP_TEMPLATE_VIS bit_xor<void>
-{
-    template <class _T1, class _T2>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_T1&& __t, _T2&& __u) const
-    _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) ^ _VSTD::forward<_T2>(__u)))
-    -> decltype        (_VSTD::forward<_T1>(__t) ^ _VSTD::forward<_T2>(__u))
-        { return        _VSTD::forward<_T1>(__t) ^ _VSTD::forward<_T2>(__u); }
-    typedef void is_transparent;
-};
-#endif
-
-
-#if _LIBCPP_STD_VER > 11
-_LIBCPP_SUPPRESS_DEPRECATED_PUSH
-template <class _Tp = void>
-struct _LIBCPP_TEMPLATE_VIS bit_not
-#if !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : unary_function<_Tp, _Tp>
-#endif
-{
-_LIBCPP_SUPPRESS_DEPRECATED_POP
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp result_type;
-    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp argument_type;
-#endif
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    _Tp operator()(const _Tp& __x) const
-        {return ~__x;}
-};
-
-template <>
-struct _LIBCPP_TEMPLATE_VIS bit_not<void>
-{
-    template <class _Tp>
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    auto operator()(_Tp&& __x) const
-    _NOEXCEPT_(noexcept(~_VSTD::forward<_Tp>(__x)))
-    -> decltype        (~_VSTD::forward<_Tp>(__x))
-        { return        ~_VSTD::forward<_Tp>(__x); }
-    typedef void is_transparent;
-};
-#endif
-
-#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS)
-template <class _Predicate>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 unary_negate
-    : public unary_function<typename _Predicate::argument_type, bool>
-{
-    _Predicate __pred_;
-public:
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    explicit unary_negate(const _Predicate& __pred)
-        : __pred_(__pred) {}
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const typename _Predicate::argument_type& __x) const
-        {return !__pred_(__x);}
-};
-
-template <class _Predicate>
-_LIBCPP_DEPRECATED_IN_CXX17 inline _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-unary_negate<_Predicate>
-not1(const _Predicate& __pred) {return unary_negate<_Predicate>(__pred);}
-
-template <class _Predicate>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 binary_negate
-    : public binary_function<typename _Predicate::first_argument_type,
-                             typename _Predicate::second_argument_type,
-                             bool>
-{
-    _Predicate __pred_;
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit _LIBCPP_CONSTEXPR_AFTER_CXX11
-    binary_negate(const _Predicate& __pred) : __pred_(__pred) {}
-
-    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const typename _Predicate::first_argument_type& __x,
-                    const typename _Predicate::second_argument_type& __y) const
-        {return !__pred_(__x, __y);}
-};
-
-template <class _Predicate>
-_LIBCPP_DEPRECATED_IN_CXX17 inline _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-binary_negate<_Predicate>
-not2(const _Predicate& __pred) {return binary_negate<_Predicate>(__pred);}
-#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS)
-
-#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
-template <class __Operation>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 binder1st
-    : public unary_function<typename __Operation::second_argument_type,
-                            typename __Operation::result_type>
-{
-protected:
-    __Operation                               op;
-    typename __Operation::first_argument_type value;
-public:
-    _LIBCPP_INLINE_VISIBILITY binder1st(const __Operation& __x,
-                               const typename __Operation::first_argument_type __y)
-        : op(__x), value(__y) {}
-    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
-        (typename __Operation::second_argument_type& __x) const
-            {return op(value, __x);}
-    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
-        (const typename __Operation::second_argument_type& __x) const
-            {return op(value, __x);}
-};
-
-template <class __Operation, class _Tp>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-binder1st<__Operation>
-bind1st(const __Operation& __op, const _Tp& __x)
-    {return binder1st<__Operation>(__op, __x);}
-
-template <class __Operation>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 binder2nd
-    : public unary_function<typename __Operation::first_argument_type,
-                            typename __Operation::result_type>
-{
-protected:
-    __Operation                                op;
-    typename __Operation::second_argument_type value;
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    binder2nd(const __Operation& __x, const typename __Operation::second_argument_type __y)
-        : op(__x), value(__y) {}
-    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
-        (      typename __Operation::first_argument_type& __x) const
-            {return op(__x, value);}
-    _LIBCPP_INLINE_VISIBILITY typename __Operation::result_type operator()
-        (const typename __Operation::first_argument_type& __x) const
-            {return op(__x, value);}
-};
-
-template <class __Operation, class _Tp>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-binder2nd<__Operation>
-bind2nd(const __Operation& __op, const _Tp& __x)
-    {return binder2nd<__Operation>(__op, __x);}
-
-template <class _Arg, class _Result>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 pointer_to_unary_function
-    : public unary_function<_Arg, _Result>
-{
-    _Result (*__f_)(_Arg);
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit pointer_to_unary_function(_Result (*__f)(_Arg))
-        : __f_(__f) {}
-    _LIBCPP_INLINE_VISIBILITY _Result operator()(_Arg __x) const
-        {return __f_(__x);}
-};
-
-template <class _Arg, class _Result>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-pointer_to_unary_function<_Arg,_Result>
-ptr_fun(_Result (*__f)(_Arg))
-    {return pointer_to_unary_function<_Arg,_Result>(__f);}
-
-template <class _Arg1, class _Arg2, class _Result>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 pointer_to_binary_function
-    : public binary_function<_Arg1, _Arg2, _Result>
-{
-    _Result (*__f_)(_Arg1, _Arg2);
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit pointer_to_binary_function(_Result (*__f)(_Arg1, _Arg2))
-        : __f_(__f) {}
-    _LIBCPP_INLINE_VISIBILITY _Result operator()(_Arg1 __x, _Arg2 __y) const
-        {return __f_(__x, __y);}
-};
-
-template <class _Arg1, class _Arg2, class _Result>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-pointer_to_binary_function<_Arg1,_Arg2,_Result>
-ptr_fun(_Result (*__f)(_Arg1,_Arg2))
-    {return pointer_to_binary_function<_Arg1,_Arg2,_Result>(__f);}
-
-template<class _Sp, class _Tp>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun_t
-    : public unary_function<_Tp*, _Sp>
-{
-    _Sp (_Tp::*__p_)();
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit mem_fun_t(_Sp (_Tp::*__p)())
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp* __p) const
-        {return (__p->*__p_)();}
-};
-
-template<class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun1_t
-    : public binary_function<_Tp*, _Ap, _Sp>
-{
-    _Sp (_Tp::*__p_)(_Ap);
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit mem_fun1_t(_Sp (_Tp::*__p)(_Ap))
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp* __p, _Ap __x) const
-        {return (__p->*__p_)(__x);}
-};
-
-template<class _Sp, class _Tp>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-mem_fun_t<_Sp,_Tp>
-mem_fun(_Sp (_Tp::*__f)())
-    {return mem_fun_t<_Sp,_Tp>(__f);}
-
-template<class _Sp, class _Tp, class _Ap>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-mem_fun1_t<_Sp,_Tp,_Ap>
-mem_fun(_Sp (_Tp::*__f)(_Ap))
-    {return mem_fun1_t<_Sp,_Tp,_Ap>(__f);}
-
-template<class _Sp, class _Tp>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun_ref_t
-    : public unary_function<_Tp, _Sp>
-{
-    _Sp (_Tp::*__p_)();
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit mem_fun_ref_t(_Sp (_Tp::*__p)())
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp& __p) const
-        {return (__p.*__p_)();}
-};
-
-template<class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 mem_fun1_ref_t
-    : public binary_function<_Tp, _Ap, _Sp>
-{
-    _Sp (_Tp::*__p_)(_Ap);
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit mem_fun1_ref_t(_Sp (_Tp::*__p)(_Ap))
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(_Tp& __p, _Ap __x) const
-        {return (__p.*__p_)(__x);}
-};
-
-template<class _Sp, class _Tp>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-mem_fun_ref_t<_Sp,_Tp>
-mem_fun_ref(_Sp (_Tp::*__f)())
-    {return mem_fun_ref_t<_Sp,_Tp>(__f);}
-
-template<class _Sp, class _Tp, class _Ap>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-mem_fun1_ref_t<_Sp,_Tp,_Ap>
-mem_fun_ref(_Sp (_Tp::*__f)(_Ap))
-    {return mem_fun1_ref_t<_Sp,_Tp,_Ap>(__f);}
-
-template <class _Sp, class _Tp>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun_t
-    : public unary_function<const _Tp*, _Sp>
-{
-    _Sp (_Tp::*__p_)() const;
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun_t(_Sp (_Tp::*__p)() const)
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp* __p) const
-        {return (__p->*__p_)();}
-};
-
-template <class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun1_t
-    : public binary_function<const _Tp*, _Ap, _Sp>
-{
-    _Sp (_Tp::*__p_)(_Ap) const;
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun1_t(_Sp (_Tp::*__p)(_Ap) const)
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp* __p, _Ap __x) const
-        {return (__p->*__p_)(__x);}
-};
-
-template <class _Sp, class _Tp>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-const_mem_fun_t<_Sp,_Tp>
-mem_fun(_Sp (_Tp::*__f)() const)
-    {return const_mem_fun_t<_Sp,_Tp>(__f);}
-
-template <class _Sp, class _Tp, class _Ap>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-const_mem_fun1_t<_Sp,_Tp,_Ap>
-mem_fun(_Sp (_Tp::*__f)(_Ap) const)
-    {return const_mem_fun1_t<_Sp,_Tp,_Ap>(__f);}
-
-template <class _Sp, class _Tp>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun_ref_t
-    : public unary_function<_Tp, _Sp>
-{
-    _Sp (_Tp::*__p_)() const;
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun_ref_t(_Sp (_Tp::*__p)() const)
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp& __p) const
-        {return (__p.*__p_)();}
-};
-
-template <class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 const_mem_fun1_ref_t
-    : public binary_function<_Tp, _Ap, _Sp>
-{
-    _Sp (_Tp::*__p_)(_Ap) const;
-public:
-    _LIBCPP_INLINE_VISIBILITY explicit const_mem_fun1_ref_t(_Sp (_Tp::*__p)(_Ap) const)
-        : __p_(__p) {}
-    _LIBCPP_INLINE_VISIBILITY _Sp operator()(const _Tp& __p, _Ap __x) const
-        {return (__p.*__p_)(__x);}
-};
-
-template <class _Sp, class _Tp>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-const_mem_fun_ref_t<_Sp,_Tp>
-mem_fun_ref(_Sp (_Tp::*__f)() const)
-    {return const_mem_fun_ref_t<_Sp,_Tp>(__f);}
-
-template <class _Sp, class _Tp, class _Ap>
-_LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
-const_mem_fun1_ref_t<_Sp,_Tp,_Ap>
-mem_fun_ref(_Sp (_Tp::*__f)(_Ap) const)
-    {return const_mem_fun1_ref_t<_Sp,_Tp,_Ap>(__f);}
-#endif
-
-////////////////////////////////////////////////////////////////////////////////
-//                                MEMFUN
-//==============================================================================
-
-template <class _Tp>
-class __mem_fn
-#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : public __weak_result_type<_Tp>
-#endif
-{
-public:
-    // types
-    typedef _Tp type;
-private:
-    type __f_;
-
-public:
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    __mem_fn(type __f) _NOEXCEPT : __f_(__f) {}
-
-#ifndef _LIBCPP_CXX03_LANG
-    // invoke
-    template <class... _ArgTypes>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    typename __invoke_return<type, _ArgTypes...>::type
-    operator() (_ArgTypes&&... __args) const {
-        return _VSTD::__invoke(__f_, _VSTD::forward<_ArgTypes>(__args)...);
-    }
-#else
-
-    template <class _A0>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return0<type, _A0>::type
-    operator() (_A0& __a0) const {
-        return _VSTD::__invoke(__f_, __a0);
-    }
-
-    template <class _A0>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return0<type, _A0 const>::type
-    operator() (_A0 const& __a0) const {
-        return _VSTD::__invoke(__f_, __a0);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0, _A1>::type
-    operator() (_A0& __a0, _A1& __a1) const {
-        return _VSTD::__invoke(__f_, __a0, __a1);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0 const, _A1>::type
-    operator() (_A0 const& __a0, _A1& __a1) const {
-        return _VSTD::__invoke(__f_, __a0, __a1);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0, _A1 const>::type
-    operator() (_A0& __a0, _A1 const& __a1) const {
-        return _VSTD::__invoke(__f_, __a0, __a1);
-    }
-
-    template <class _A0, class _A1>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return1<type, _A0 const, _A1 const>::type
-    operator() (_A0 const& __a0, _A1 const& __a1) const {
-        return _VSTD::__invoke(__f_, __a0, __a1);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1, _A2>::type
-    operator() (_A0& __a0, _A1& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1, _A2>::type
-    operator() (_A0 const& __a0, _A1& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1 const, _A2>::type
-    operator() (_A0& __a0, _A1 const& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1, _A2 const>::type
-    operator() (_A0& __a0, _A1& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1 const, _A2>::type
-    operator() (_A0 const& __a0, _A1 const& __a1, _A2& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1, _A2 const>::type
-    operator() (_A0 const& __a0, _A1& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0, _A1 const, _A2 const>::type
-    operator() (_A0& __a0, _A1 const& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-
-    template <class _A0, class _A1, class _A2>
-    _LIBCPP_INLINE_VISIBILITY
-    typename __invoke_return2<type, _A0 const, _A1 const, _A2 const>::type
-    operator() (_A0 const& __a0, _A1 const& __a1, _A2 const& __a2) const {
-        return _VSTD::__invoke(__f_, __a0, __a1, __a2);
-    }
-#endif
-};
-
-template<class _Rp, class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-__mem_fn<_Rp _Tp::*>
-mem_fn(_Rp _Tp::* __pm) _NOEXCEPT
-{
-    return __mem_fn<_Rp _Tp::*>(__pm);
-}
-
-////////////////////////////////////////////////////////////////////////////////
-//                                FUNCTION
-//==============================================================================
-
-// bad_function_call
-
-class _LIBCPP_EXCEPTION_ABI bad_function_call
-    : public exception
-{
-#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
-public:
-    virtual ~bad_function_call() _NOEXCEPT;
-
-    virtual const char* what() const _NOEXCEPT;
-#endif
-};
-
-_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
-void __throw_bad_function_call()
-{
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw bad_function_call();
-#else
-    _VSTD::abort();
-#endif
-}
-
-#if defined(_LIBCPP_CXX03_LANG) && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS) && __has_attribute(deprecated)
-#   define _LIBCPP_DEPRECATED_CXX03_FUNCTION \
-        __attribute__((deprecated("Using std::function in C++03 is not supported anymore. Please upgrade to C++11 or later, or use a different type")))
-#else
-#   define _LIBCPP_DEPRECATED_CXX03_FUNCTION /* nothing */
-#endif
-
-template<class _Fp> class _LIBCPP_DEPRECATED_CXX03_FUNCTION _LIBCPP_TEMPLATE_VIS function; // undefined
-
-namespace __function
-{
-
-template<class _Rp>
-struct __maybe_derive_from_unary_function
-{
-};
-
-template<class _Rp, class _A1>
-struct __maybe_derive_from_unary_function<_Rp(_A1)>
-    : public unary_function<_A1, _Rp>
-{
-};
-
-template<class _Rp>
-struct __maybe_derive_from_binary_function
-{
-};
-
-template<class _Rp, class _A1, class _A2>
-struct __maybe_derive_from_binary_function<_Rp(_A1, _A2)>
-    : public binary_function<_A1, _A2, _Rp>
-{
-};
-
-template <class _Fp>
-_LIBCPP_INLINE_VISIBILITY
-bool __not_null(_Fp const&) { return true; }
-
-template <class _Fp>
-_LIBCPP_INLINE_VISIBILITY
-bool __not_null(_Fp* __ptr) { return __ptr; }
-
-template <class _Ret, class _Class>
-_LIBCPP_INLINE_VISIBILITY
-bool __not_null(_Ret _Class::*__ptr) { return __ptr; }
-
-template <class _Fp>
-_LIBCPP_INLINE_VISIBILITY
-bool __not_null(function<_Fp> const& __f) { return !!__f; }
-
-#ifdef _LIBCPP_HAS_EXTENSION_BLOCKS
-template <class _Rp, class ..._Args>
-_LIBCPP_INLINE_VISIBILITY
-bool __not_null(_Rp (^__p)(_Args...)) { return __p; }
-#endif
-
-} // namespace __function
-
-#ifndef _LIBCPP_CXX03_LANG
-
-namespace __function {
-
-// __alloc_func holds a functor and an allocator.
-
-template <class _Fp, class _Ap, class _FB> class __alloc_func;
-template <class _Fp, class _FB>
-class __default_alloc_func;
-
-template <class _Fp, class _Ap, class _Rp, class... _ArgTypes>
-class __alloc_func<_Fp, _Ap, _Rp(_ArgTypes...)>
-{
-    __compressed_pair<_Fp, _Ap> __f_;
-
-  public:
-    typedef _LIBCPP_NODEBUG_TYPE _Fp _Target;
-    typedef _LIBCPP_NODEBUG_TYPE _Ap _Alloc;
-
-    _LIBCPP_INLINE_VISIBILITY
-    const _Target& __target() const { return __f_.first(); }
-
-    // WIN32 APIs may define __allocator, so use __get_allocator instead.
-    _LIBCPP_INLINE_VISIBILITY
-    const _Alloc& __get_allocator() const { return __f_.second(); }
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __alloc_func(_Target&& __f)
-        : __f_(piecewise_construct, _VSTD::forward_as_tuple(_VSTD::move(__f)),
-               _VSTD::forward_as_tuple())
-    {
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __alloc_func(const _Target& __f, const _Alloc& __a)
-        : __f_(piecewise_construct, _VSTD::forward_as_tuple(__f),
-               _VSTD::forward_as_tuple(__a))
-    {
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __alloc_func(const _Target& __f, _Alloc&& __a)
-        : __f_(piecewise_construct, _VSTD::forward_as_tuple(__f),
-               _VSTD::forward_as_tuple(_VSTD::move(__a)))
-    {
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __alloc_func(_Target&& __f, _Alloc&& __a)
-        : __f_(piecewise_construct, _VSTD::forward_as_tuple(_VSTD::move(__f)),
-               _VSTD::forward_as_tuple(_VSTD::move(__a)))
-    {
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    _Rp operator()(_ArgTypes&&... __arg)
-    {
-        typedef __invoke_void_return_wrapper<_Rp> _Invoker;
-        return _Invoker::__call(__f_.first(),
-                                _VSTD::forward<_ArgTypes>(__arg)...);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __alloc_func* __clone() const
-    {
-        typedef allocator_traits<_Alloc> __alloc_traits;
-        typedef
-            typename __rebind_alloc_helper<__alloc_traits, __alloc_func>::type
-                _AA;
-        _AA __a(__f_.second());
-        typedef __allocator_destructor<_AA> _Dp;
-        unique_ptr<__alloc_func, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
-        ::new ((void*)__hold.get()) __alloc_func(__f_.first(), _Alloc(__a));
-        return __hold.release();
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void destroy() _NOEXCEPT { __f_.~__compressed_pair<_Target, _Alloc>(); }
-
-    static void __destroy_and_delete(__alloc_func* __f) {
-      typedef allocator_traits<_Alloc> __alloc_traits;
-      typedef typename __rebind_alloc_helper<__alloc_traits, __alloc_func>::type
-          _FunAlloc;
-      _FunAlloc __a(__f->__get_allocator());
-      __f->destroy();
-      __a.deallocate(__f, 1);
-    }
-};
-
-template <class _Fp, class _Rp, class... _ArgTypes>
-class __default_alloc_func<_Fp, _Rp(_ArgTypes...)> {
-  _Fp __f_;
-
-public:
-  typedef _LIBCPP_NODEBUG_TYPE _Fp _Target;
-
-  _LIBCPP_INLINE_VISIBILITY
-  const _Target& __target() const { return __f_; }
-
-  _LIBCPP_INLINE_VISIBILITY
-  explicit __default_alloc_func(_Target&& __f) : __f_(_VSTD::move(__f)) {}
-
-  _LIBCPP_INLINE_VISIBILITY
-  explicit __default_alloc_func(const _Target& __f) : __f_(__f) {}
-
-  _LIBCPP_INLINE_VISIBILITY
-  _Rp operator()(_ArgTypes&&... __arg) {
-    typedef __invoke_void_return_wrapper<_Rp> _Invoker;
-    return _Invoker::__call(__f_, _VSTD::forward<_ArgTypes>(__arg)...);
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  __default_alloc_func* __clone() const {
-      __builtin_new_allocator::__holder_t __hold =
-        __builtin_new_allocator::__allocate_type<__default_alloc_func>(1);
-    __default_alloc_func* __res =
-        ::new ((void*)__hold.get()) __default_alloc_func(__f_);
-    (void)__hold.release();
-    return __res;
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  void destroy() _NOEXCEPT { __f_.~_Target(); }
-
-  static void __destroy_and_delete(__default_alloc_func* __f) {
-    __f->destroy();
-      __builtin_new_allocator::__deallocate_type<__default_alloc_func>(__f, 1);
-  }
-};
-
-// __base provides an abstract interface for copyable functors.
-
-template<class _Fp> class _LIBCPP_TEMPLATE_VIS __base;
-
-template<class _Rp, class ..._ArgTypes>
-class __base<_Rp(_ArgTypes...)>
-{
-    __base(const __base&);
-    __base& operator=(const __base&);
-public:
-    _LIBCPP_INLINE_VISIBILITY __base() {}
-    _LIBCPP_INLINE_VISIBILITY virtual ~__base() {}
-    virtual __base* __clone() const = 0;
-    virtual void __clone(__base*) const = 0;
-    virtual void destroy() _NOEXCEPT = 0;
-    virtual void destroy_deallocate() _NOEXCEPT = 0;
-    virtual _Rp operator()(_ArgTypes&& ...) = 0;
-#ifndef _LIBCPP_NO_RTTI
-    virtual const void* target(const type_info&) const _NOEXCEPT = 0;
-    virtual const std::type_info& target_type() const _NOEXCEPT = 0;
-#endif // _LIBCPP_NO_RTTI
-};
-
-// __func implements __base for a given functor type.
-
-template<class _FD, class _Alloc, class _FB> class __func;
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-class __func<_Fp, _Alloc, _Rp(_ArgTypes...)>
-    : public  __base<_Rp(_ArgTypes...)>
-{
-    __alloc_func<_Fp, _Alloc, _Rp(_ArgTypes...)> __f_;
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __func(_Fp&& __f)
-        : __f_(_VSTD::move(__f)) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __func(const _Fp& __f, const _Alloc& __a)
-        : __f_(__f, __a) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __func(const _Fp& __f, _Alloc&& __a)
-        : __f_(__f, _VSTD::move(__a)) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __func(_Fp&& __f, _Alloc&& __a)
-        : __f_(_VSTD::move(__f), _VSTD::move(__a)) {}
-
-    virtual __base<_Rp(_ArgTypes...)>* __clone() const;
-    virtual void __clone(__base<_Rp(_ArgTypes...)>*) const;
-    virtual void destroy() _NOEXCEPT;
-    virtual void destroy_deallocate() _NOEXCEPT;
-    virtual _Rp operator()(_ArgTypes&&... __arg);
-#ifndef _LIBCPP_NO_RTTI
-    virtual const void* target(const type_info&) const _NOEXCEPT;
-    virtual const std::type_info& target_type() const _NOEXCEPT;
-#endif // _LIBCPP_NO_RTTI
-};
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-__base<_Rp(_ArgTypes...)>*
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::__clone() const
-{
-    typedef allocator_traits<_Alloc> __alloc_traits;
-    typedef typename __rebind_alloc_helper<__alloc_traits, __func>::type _Ap;
-    _Ap __a(__f_.__get_allocator());
-    typedef __allocator_destructor<_Ap> _Dp;
-    unique_ptr<__func, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
-    ::new ((void*)__hold.get()) __func(__f_.__target(), _Alloc(__a));
-    return __hold.release();
-}
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-void
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::__clone(__base<_Rp(_ArgTypes...)>* __p) const
-{
-    ::new ((void*)__p) __func(__f_.__target(), __f_.__get_allocator());
-}
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-void
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::destroy() _NOEXCEPT
-{
-    __f_.destroy();
-}
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-void
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::destroy_deallocate() _NOEXCEPT
-{
-    typedef allocator_traits<_Alloc> __alloc_traits;
-    typedef typename __rebind_alloc_helper<__alloc_traits, __func>::type _Ap;
-    _Ap __a(__f_.__get_allocator());
-    __f_.destroy();
-    __a.deallocate(this, 1);
-}
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-_Rp
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::operator()(_ArgTypes&& ... __arg)
-{
-    return __f_(_VSTD::forward<_ArgTypes>(__arg)...);
-}
-
-#ifndef _LIBCPP_NO_RTTI
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-const void*
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target(const type_info& __ti) const _NOEXCEPT
-{
-    if (__ti == typeid(_Fp))
-        return &__f_.__target();
-    return nullptr;
-}
-
-template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-const std::type_info&
-__func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target_type() const _NOEXCEPT
-{
-    return typeid(_Fp);
-}
-
-#endif // _LIBCPP_NO_RTTI
-
-// __value_func creates a value-type from a __func.
-
-template <class _Fp> class __value_func;
-
-template <class _Rp, class... _ArgTypes> class __value_func<_Rp(_ArgTypes...)>
-{
-    typename aligned_storage<3 * sizeof(void*)>::type __buf_;
-
-    typedef __base<_Rp(_ArgTypes...)> __func;
-    __func* __f_;
-
-    _LIBCPP_NO_CFI static __func* __as_base(void* p)
-    {
-        return reinterpret_cast<__func*>(p);
-    }
-
-  public:
-    _LIBCPP_INLINE_VISIBILITY
-    __value_func() _NOEXCEPT : __f_(nullptr) {}
-
-    template <class _Fp, class _Alloc>
-    _LIBCPP_INLINE_VISIBILITY __value_func(_Fp&& __f, const _Alloc& __a)
-        : __f_(nullptr)
-    {
-        typedef allocator_traits<_Alloc> __alloc_traits;
-        typedef __function::__func<_Fp, _Alloc, _Rp(_ArgTypes...)> _Fun;
-        typedef typename __rebind_alloc_helper<__alloc_traits, _Fun>::type
-            _FunAlloc;
-
-        if (__function::__not_null(__f))
-        {
-            _FunAlloc __af(__a);
-            if (sizeof(_Fun) <= sizeof(__buf_) &&
-                is_nothrow_copy_constructible<_Fp>::value &&
-                is_nothrow_copy_constructible<_FunAlloc>::value)
-            {
-                __f_ =
-                    ::new ((void*)&__buf_) _Fun(_VSTD::move(__f), _Alloc(__af));
-            }
-            else
-            {
-                typedef __allocator_destructor<_FunAlloc> _Dp;
-                unique_ptr<__func, _Dp> __hold(__af.allocate(1), _Dp(__af, 1));
-                ::new ((void*)__hold.get()) _Fun(_VSTD::move(__f), _Alloc(__a));
-                __f_ = __hold.release();
-            }
-        }
-    }
-
-    template <class _Fp,
-        class = typename enable_if<!is_same<typename decay<_Fp>::type, __value_func>::value>::type>
-    _LIBCPP_INLINE_VISIBILITY explicit __value_func(_Fp&& __f)
-        : __value_func(_VSTD::forward<_Fp>(__f), allocator<_Fp>()) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __value_func(const __value_func& __f)
-    {
-        if (__f.__f_ == nullptr)
-            __f_ = nullptr;
-        else if ((void*)__f.__f_ == &__f.__buf_)
-        {
-            __f_ = __as_base(&__buf_);
-            __f.__f_->__clone(__f_);
-        }
-        else
-            __f_ = __f.__f_->__clone();
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __value_func(__value_func&& __f) _NOEXCEPT
-    {
-        if (__f.__f_ == nullptr)
-            __f_ = nullptr;
-        else if ((void*)__f.__f_ == &__f.__buf_)
-        {
-            __f_ = __as_base(&__buf_);
-            __f.__f_->__clone(__f_);
-        }
-        else
-        {
-            __f_ = __f.__f_;
-            __f.__f_ = nullptr;
-        }
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    ~__value_func()
-    {
-        if ((void*)__f_ == &__buf_)
-            __f_->destroy();
-        else if (__f_)
-            __f_->destroy_deallocate();
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __value_func& operator=(__value_func&& __f)
-    {
-        *this = nullptr;
-        if (__f.__f_ == nullptr)
-            __f_ = nullptr;
-        else if ((void*)__f.__f_ == &__f.__buf_)
-        {
-            __f_ = __as_base(&__buf_);
-            __f.__f_->__clone(__f_);
-        }
-        else
-        {
-            __f_ = __f.__f_;
-            __f.__f_ = nullptr;
-        }
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __value_func& operator=(nullptr_t)
-    {
-        __func* __f = __f_;
-        __f_ = nullptr;
-        if ((void*)__f == &__buf_)
-            __f->destroy();
-        else if (__f)
-            __f->destroy_deallocate();
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    _Rp operator()(_ArgTypes&&... __args) const
-    {
-        if (__f_ == nullptr)
-            __throw_bad_function_call();
-        return (*__f_)(_VSTD::forward<_ArgTypes>(__args)...);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void swap(__value_func& __f) _NOEXCEPT
-    {
-        if (&__f == this)
-            return;
-        if ((void*)__f_ == &__buf_ && (void*)__f.__f_ == &__f.__buf_)
-        {
-            typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
-            __func* __t = __as_base(&__tempbuf);
-            __f_->__clone(__t);
-            __f_->destroy();
-            __f_ = nullptr;
-            __f.__f_->__clone(__as_base(&__buf_));
-            __f.__f_->destroy();
-            __f.__f_ = nullptr;
-            __f_ = __as_base(&__buf_);
-            __t->__clone(__as_base(&__f.__buf_));
-            __t->destroy();
-            __f.__f_ = __as_base(&__f.__buf_);
-        }
-        else if ((void*)__f_ == &__buf_)
-        {
-            __f_->__clone(__as_base(&__f.__buf_));
-            __f_->destroy();
-            __f_ = __f.__f_;
-            __f.__f_ = __as_base(&__f.__buf_);
-        }
-        else if ((void*)__f.__f_ == &__f.__buf_)
-        {
-            __f.__f_->__clone(__as_base(&__buf_));
-            __f.__f_->destroy();
-            __f.__f_ = __f_;
-            __f_ = __as_base(&__buf_);
-        }
-        else
-            _VSTD::swap(__f_, __f.__f_);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit operator bool() const _NOEXCEPT { return __f_ != nullptr; }
-
-#ifndef _LIBCPP_NO_RTTI
-    _LIBCPP_INLINE_VISIBILITY
-    const std::type_info& target_type() const _NOEXCEPT
-    {
-        if (__f_ == nullptr)
-            return typeid(void);
-        return __f_->target_type();
-    }
-
-    template <typename _Tp>
-    _LIBCPP_INLINE_VISIBILITY const _Tp* target() const _NOEXCEPT
-    {
-        if (__f_ == nullptr)
-            return nullptr;
-        return (const _Tp*)__f_->target(typeid(_Tp));
-    }
-#endif // _LIBCPP_NO_RTTI
-};
-
-// Storage for a functor object, to be used with __policy to manage copy and
-// destruction.
-union __policy_storage
-{
-    mutable char __small[sizeof(void*) * 2];
-    void* __large;
-};
-
-// True if _Fun can safely be held in __policy_storage.__small.
-template <typename _Fun>
-struct __use_small_storage
-    : public integral_constant<
-          bool, sizeof(_Fun) <= sizeof(__policy_storage) &&
-                    _LIBCPP_ALIGNOF(_Fun) <= _LIBCPP_ALIGNOF(__policy_storage) &&
-                    is_trivially_copy_constructible<_Fun>::value &&
-                    is_trivially_destructible<_Fun>::value> {};
-
-// Policy contains information about how to copy, destroy, and move the
-// underlying functor. You can think of it as a vtable of sorts.
-struct __policy
-{
-    // Used to copy or destroy __large values. null for trivial objects.
-    void* (*const __clone)(const void*);
-    void (*const __destroy)(void*);
-
-    // True if this is the null policy (no value).
-    const bool __is_null;
-
-    // The target type. May be null if RTTI is disabled.
-    const std::type_info* const __type_info;
-
-    // Returns a pointer to a static policy object suitable for the functor
-    // type.
-    template <typename _Fun>
-    _LIBCPP_INLINE_VISIBILITY static const __policy* __create()
-    {
-        return __choose_policy<_Fun>(__use_small_storage<_Fun>());
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    static const __policy* __create_empty()
-    {
-        static const _LIBCPP_CONSTEXPR __policy __policy_ = {nullptr, nullptr,
-                                                             true,
-#ifndef _LIBCPP_NO_RTTI
-                                                             &typeid(void)
-#else
-                                                             nullptr
-#endif
-        };
-        return &__policy_;
-    }
-
-  private:
-    template <typename _Fun> static void* __large_clone(const void* __s)
-    {
-        const _Fun* __f = static_cast<const _Fun*>(__s);
-        return __f->__clone();
-    }
-
-    template <typename _Fun>
-    static void __large_destroy(void* __s) {
-      _Fun::__destroy_and_delete(static_cast<_Fun*>(__s));
-    }
-
-    template <typename _Fun>
-    _LIBCPP_INLINE_VISIBILITY static const __policy*
-    __choose_policy(/* is_small = */ false_type) {
-      static const _LIBCPP_CONSTEXPR __policy __policy_ = {
-          &__large_clone<_Fun>, &__large_destroy<_Fun>, false,
-#ifndef _LIBCPP_NO_RTTI
-          &typeid(typename _Fun::_Target)
-#else
-          nullptr
-#endif
-      };
-        return &__policy_;
-    }
-
-    template <typename _Fun>
-    _LIBCPP_INLINE_VISIBILITY static const __policy*
-        __choose_policy(/* is_small = */ true_type)
-    {
-        static const _LIBCPP_CONSTEXPR __policy __policy_ = {
-            nullptr, nullptr, false,
-#ifndef _LIBCPP_NO_RTTI
-            &typeid(typename _Fun::_Target)
-#else
-            nullptr
-#endif
-        };
-        return &__policy_;
-    }
-};
-
-// Used to choose between perfect forwarding or pass-by-value. Pass-by-value is
-// faster for types that can be passed in registers.
-template <typename _Tp>
-using __fast_forward =
-    typename conditional<is_scalar<_Tp>::value, _Tp, _Tp&&>::type;
-
-// __policy_invoker calls an instance of __alloc_func held in __policy_storage.
-
-template <class _Fp> struct __policy_invoker;
-
-template <class _Rp, class... _ArgTypes>
-struct __policy_invoker<_Rp(_ArgTypes...)>
-{
-    typedef _Rp (*__Call)(const __policy_storage*,
-                          __fast_forward<_ArgTypes>...);
-
-    __Call __call_;
-
-    // Creates an invoker that throws bad_function_call.
-    _LIBCPP_INLINE_VISIBILITY
-    __policy_invoker() : __call_(&__call_empty) {}
-
-    // Creates an invoker that calls the given instance of __func.
-    template <typename _Fun>
-    _LIBCPP_INLINE_VISIBILITY static __policy_invoker __create()
-    {
-        return __policy_invoker(&__call_impl<_Fun>);
-    }
-
-  private:
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __policy_invoker(__Call __c) : __call_(__c) {}
-
-    static _Rp __call_empty(const __policy_storage*,
-                            __fast_forward<_ArgTypes>...)
-    {
-        __throw_bad_function_call();
-    }
-
-    template <typename _Fun>
-    static _Rp __call_impl(const __policy_storage* __buf,
-                           __fast_forward<_ArgTypes>... __args)
-    {
-        _Fun* __f = reinterpret_cast<_Fun*>(__use_small_storage<_Fun>::value
-                                                ? &__buf->__small
-                                                : __buf->__large);
-        return (*__f)(_VSTD::forward<_ArgTypes>(__args)...);
-    }
-};
-
-// __policy_func uses a __policy and __policy_invoker to create a type-erased,
-// copyable functor.
-
-template <class _Fp> class __policy_func;
-
-template <class _Rp, class... _ArgTypes> class __policy_func<_Rp(_ArgTypes...)>
-{
-    // Inline storage for small objects.
-    __policy_storage __buf_;
-
-    // Calls the value stored in __buf_. This could technically be part of
-    // policy, but storing it here eliminates a level of indirection inside
-    // operator().
-    typedef __function::__policy_invoker<_Rp(_ArgTypes...)> __invoker;
-    __invoker __invoker_;
-
-    // The policy that describes how to move / copy / destroy __buf_. Never
-    // null, even if the function is empty.
-    const __policy* __policy_;
-
-  public:
-    _LIBCPP_INLINE_VISIBILITY
-    __policy_func() : __policy_(__policy::__create_empty()) {}
-
-    template <class _Fp, class _Alloc>
-    _LIBCPP_INLINE_VISIBILITY __policy_func(_Fp&& __f, const _Alloc& __a)
-        : __policy_(__policy::__create_empty())
-    {
-        typedef __alloc_func<_Fp, _Alloc, _Rp(_ArgTypes...)> _Fun;
-        typedef allocator_traits<_Alloc> __alloc_traits;
-        typedef typename __rebind_alloc_helper<__alloc_traits, _Fun>::type
-            _FunAlloc;
-
-        if (__function::__not_null(__f))
-        {
-            __invoker_ = __invoker::template __create<_Fun>();
-            __policy_ = __policy::__create<_Fun>();
-
-            _FunAlloc __af(__a);
-            if (__use_small_storage<_Fun>())
-            {
-                ::new ((void*)&__buf_.__small)
-                    _Fun(_VSTD::move(__f), _Alloc(__af));
-            }
-            else
-            {
-                typedef __allocator_destructor<_FunAlloc> _Dp;
-                unique_ptr<_Fun, _Dp> __hold(__af.allocate(1), _Dp(__af, 1));
-                ::new ((void*)__hold.get())
-                    _Fun(_VSTD::move(__f), _Alloc(__af));
-                __buf_.__large = __hold.release();
-            }
-        }
-    }
-
-    template <class _Fp, class = typename enable_if<!is_same<typename decay<_Fp>::type, __policy_func>::value>::type>
-    _LIBCPP_INLINE_VISIBILITY explicit __policy_func(_Fp&& __f)
-        : __policy_(__policy::__create_empty()) {
-      typedef __default_alloc_func<_Fp, _Rp(_ArgTypes...)> _Fun;
-
-      if (__function::__not_null(__f)) {
-        __invoker_ = __invoker::template __create<_Fun>();
-        __policy_ = __policy::__create<_Fun>();
-        if (__use_small_storage<_Fun>()) {
-          ::new ((void*)&__buf_.__small) _Fun(_VSTD::move(__f));
-        } else {
-          __builtin_new_allocator::__holder_t __hold =
-              __builtin_new_allocator::__allocate_type<_Fun>(1);
-          __buf_.__large = ::new ((void*)__hold.get()) _Fun(_VSTD::move(__f));
-          (void)__hold.release();
-        }
-      }
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __policy_func(const __policy_func& __f)
-        : __buf_(__f.__buf_), __invoker_(__f.__invoker_),
-          __policy_(__f.__policy_)
-    {
-        if (__policy_->__clone)
-            __buf_.__large = __policy_->__clone(__f.__buf_.__large);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __policy_func(__policy_func&& __f)
-        : __buf_(__f.__buf_), __invoker_(__f.__invoker_),
-          __policy_(__f.__policy_)
-    {
-        if (__policy_->__destroy)
-        {
-            __f.__policy_ = __policy::__create_empty();
-            __f.__invoker_ = __invoker();
-        }
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    ~__policy_func()
-    {
-        if (__policy_->__destroy)
-            __policy_->__destroy(__buf_.__large);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __policy_func& operator=(__policy_func&& __f)
-    {
-        *this = nullptr;
-        __buf_ = __f.__buf_;
-        __invoker_ = __f.__invoker_;
-        __policy_ = __f.__policy_;
-        __f.__policy_ = __policy::__create_empty();
-        __f.__invoker_ = __invoker();
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __policy_func& operator=(nullptr_t)
-    {
-        const __policy* __p = __policy_;
-        __policy_ = __policy::__create_empty();
-        __invoker_ = __invoker();
-        if (__p->__destroy)
-            __p->__destroy(__buf_.__large);
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    _Rp operator()(_ArgTypes&&... __args) const
-    {
-        return __invoker_.__call_(_VSTD::addressof(__buf_),
-                                  _VSTD::forward<_ArgTypes>(__args)...);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void swap(__policy_func& __f)
-    {
-        _VSTD::swap(__invoker_, __f.__invoker_);
-        _VSTD::swap(__policy_, __f.__policy_);
-        _VSTD::swap(__buf_, __f.__buf_);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit operator bool() const _NOEXCEPT
-    {
-        return !__policy_->__is_null;
-    }
-
-#ifndef _LIBCPP_NO_RTTI
-    _LIBCPP_INLINE_VISIBILITY
-    const std::type_info& target_type() const _NOEXCEPT
-    {
-        return *__policy_->__type_info;
-    }
-
-    template <typename _Tp>
-    _LIBCPP_INLINE_VISIBILITY const _Tp* target() const _NOEXCEPT
-    {
-        if (__policy_->__is_null || typeid(_Tp) != *__policy_->__type_info)
-            return nullptr;
-        if (__policy_->__clone) // Out of line storage.
-            return reinterpret_cast<const _Tp*>(__buf_.__large);
-        else
-            return reinterpret_cast<const _Tp*>(&__buf_.__small);
-    }
-#endif // _LIBCPP_NO_RTTI
-};
-
-#if defined(_LIBCPP_HAS_BLOCKS_RUNTIME) && !defined(_LIBCPP_HAS_OBJC_ARC)
-
-extern "C" void *_Block_copy(const void *);
-extern "C" void _Block_release(const void *);
-
-template<class _Rp1, class ..._ArgTypes1, class _Alloc, class _Rp, class ..._ArgTypes>
-class __func<_Rp1(^)(_ArgTypes1...), _Alloc, _Rp(_ArgTypes...)>
-    : public  __base<_Rp(_ArgTypes...)>
-{
-    typedef _Rp1(^__block_type)(_ArgTypes1...);
-    __block_type __f_;
-
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __func(__block_type const& __f)
-        : __f_(reinterpret_cast<__block_type>(__f ? _Block_copy(__f) : nullptr))
-    { }
-
-    // [TODO] add && to save on a retain
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __func(__block_type __f, const _Alloc& /* unused */)
-        : __f_(reinterpret_cast<__block_type>(__f ? _Block_copy(__f) : nullptr))
-    { }
-
-    virtual __base<_Rp(_ArgTypes...)>* __clone() const {
-        _LIBCPP_ASSERT(false,
-            "Block pointers are just pointers, so they should always fit into "
-            "std::function's small buffer optimization. This function should "
-            "never be invoked.");
-        return nullptr;
-    }
-
-    virtual void __clone(__base<_Rp(_ArgTypes...)>* __p) const {
-        ::new ((void*)__p) __func(__f_);
-    }
-
-    virtual void destroy() _NOEXCEPT {
-        if (__f_)
-            _Block_release(__f_);
-        __f_ = 0;
-    }
-
-    virtual void destroy_deallocate() _NOEXCEPT {
-        _LIBCPP_ASSERT(false,
-            "Block pointers are just pointers, so they should always fit into "
-            "std::function's small buffer optimization. This function should "
-            "never be invoked.");
-    }
-
-    virtual _Rp operator()(_ArgTypes&& ... __arg) {
-        return _VSTD::__invoke(__f_, _VSTD::forward<_ArgTypes>(__arg)...);
-    }
-
-#ifndef _LIBCPP_NO_RTTI
-    virtual const void* target(type_info const& __ti) const _NOEXCEPT {
-        if (__ti == typeid(__func::__block_type))
-            return &__f_;
-        return (const void*)nullptr;
-    }
-
-    virtual const std::type_info& target_type() const _NOEXCEPT {
-        return typeid(__func::__block_type);
-    }
-#endif // _LIBCPP_NO_RTTI
-};
-
-#endif // _LIBCPP_HAS_EXTENSION_BLOCKS && !_LIBCPP_HAS_OBJC_ARC
-
-}  // __function
-
-template<class _Rp, class ..._ArgTypes>
-class _LIBCPP_TEMPLATE_VIS function<_Rp(_ArgTypes...)>
-#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : public __function::__maybe_derive_from_unary_function<_Rp(_ArgTypes...)>,
-      public __function::__maybe_derive_from_binary_function<_Rp(_ArgTypes...)>
-#endif
-{
-#ifndef _LIBCPP_ABI_OPTIMIZED_FUNCTION
-    typedef __function::__value_func<_Rp(_ArgTypes...)> __func;
-#else
-    typedef __function::__policy_func<_Rp(_ArgTypes...)> __func;
-#endif
-
-    __func __f_;
-
-    template <class _Fp, bool = _And<
-        _IsNotSame<__uncvref_t<_Fp>, function>,
-        __invokable<_Fp, _ArgTypes...>
-    >::value>
-    struct __callable;
-    template <class _Fp>
-        struct __callable<_Fp, true>
-        {
-            static const bool value = is_void<_Rp>::value ||
-                __is_core_convertible<typename __invoke_of<_Fp, _ArgTypes...>::type,
-                                      _Rp>::value;
-        };
-    template <class _Fp>
-        struct __callable<_Fp, false>
-        {
-            static const bool value = false;
-        };
-
-  template <class _Fp>
-  using _EnableIfLValueCallable = typename enable_if<__callable<_Fp&>::value>::type;
-public:
-    typedef _Rp result_type;
-
-    // construct/copy/destroy:
-    _LIBCPP_INLINE_VISIBILITY
-    function() _NOEXCEPT { }
-    _LIBCPP_INLINE_VISIBILITY
-    function(nullptr_t) _NOEXCEPT {}
-    function(const function&);
-    function(function&&) _NOEXCEPT;
-    template<class _Fp, class = _EnableIfLValueCallable<_Fp>>
-    function(_Fp);
-
-#if _LIBCPP_STD_VER <= 14
-    template<class _Alloc>
-      _LIBCPP_INLINE_VISIBILITY
-      function(allocator_arg_t, const _Alloc&) _NOEXCEPT {}
-    template<class _Alloc>
-      _LIBCPP_INLINE_VISIBILITY
-      function(allocator_arg_t, const _Alloc&, nullptr_t) _NOEXCEPT {}
-    template<class _Alloc>
-      function(allocator_arg_t, const _Alloc&, const function&);
-    template<class _Alloc>
-      function(allocator_arg_t, const _Alloc&, function&&);
-    template<class _Fp, class _Alloc, class = _EnableIfLValueCallable<_Fp>>
-      function(allocator_arg_t, const _Alloc& __a, _Fp __f);
-#endif
-
-    function& operator=(const function&);
-    function& operator=(function&&) _NOEXCEPT;
-    function& operator=(nullptr_t) _NOEXCEPT;
-    template<class _Fp, class = _EnableIfLValueCallable<typename decay<_Fp>::type>>
-    function& operator=(_Fp&&);
-
-    ~function();
-
-    // function modifiers:
-    void swap(function&) _NOEXCEPT;
-
-#if _LIBCPP_STD_VER <= 14
-    template<class _Fp, class _Alloc>
-      _LIBCPP_INLINE_VISIBILITY
-      void assign(_Fp&& __f, const _Alloc& __a)
-        {function(allocator_arg, __a, _VSTD::forward<_Fp>(__f)).swap(*this);}
-#endif
-
-    // function capacity:
-    _LIBCPP_INLINE_VISIBILITY
-    explicit operator bool() const _NOEXCEPT {
-      return static_cast<bool>(__f_);
-    }
-
-    // deleted overloads close possible hole in the type system
-    template<class _R2, class... _ArgTypes2>
-      bool operator==(const function<_R2(_ArgTypes2...)>&) const = delete;
-    template<class _R2, class... _ArgTypes2>
-      bool operator!=(const function<_R2(_ArgTypes2...)>&) const = delete;
-public:
-    // function invocation:
-    _Rp operator()(_ArgTypes...) const;
-
-#ifndef _LIBCPP_NO_RTTI
-    // function target access:
-    const std::type_info& target_type() const _NOEXCEPT;
-    template <typename _Tp> _Tp* target() _NOEXCEPT;
-    template <typename _Tp> const _Tp* target() const _NOEXCEPT;
-#endif // _LIBCPP_NO_RTTI
-};
-
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
-template<class _Rp, class ..._Ap>
-function(_Rp(*)(_Ap...)) -> function<_Rp(_Ap...)>;
-
-template<class _Fp>
-struct __strip_signature;
-
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...)> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile> { using type = _Rp(_Ap...); };
-
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) &> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const &> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile &> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile &> { using type = _Rp(_Ap...); };
-
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) noexcept> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const noexcept> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile noexcept> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile noexcept> { using type = _Rp(_Ap...); };
-
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) & noexcept> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const & noexcept> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile & noexcept> { using type = _Rp(_Ap...); };
-template<class _Rp, class _Gp, class ..._Ap>
-struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile & noexcept> { using type = _Rp(_Ap...); };
-
-template<class _Fp, class _Stripped = typename __strip_signature<decltype(&_Fp::operator())>::type>
-function(_Fp) -> function<_Stripped>;
-#endif // !_LIBCPP_HAS_NO_DEDUCTION_GUIDES
-
-template<class _Rp, class ..._ArgTypes>
-function<_Rp(_ArgTypes...)>::function(const function& __f) : __f_(__f.__f_) {}
-
-#if _LIBCPP_STD_VER <= 14
-template<class _Rp, class ..._ArgTypes>
-template <class _Alloc>
-function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
-                                     const function& __f) : __f_(__f.__f_) {}
-#endif
-
-template <class _Rp, class... _ArgTypes>
-function<_Rp(_ArgTypes...)>::function(function&& __f) _NOEXCEPT
-    : __f_(_VSTD::move(__f.__f_)) {}
-
-#if _LIBCPP_STD_VER <= 14
-template<class _Rp, class ..._ArgTypes>
-template <class _Alloc>
-function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
-                                      function&& __f)
-    : __f_(_VSTD::move(__f.__f_)) {}
-#endif
-
-template <class _Rp, class... _ArgTypes>
-template <class _Fp, class>
-function<_Rp(_ArgTypes...)>::function(_Fp __f) : __f_(_VSTD::move(__f)) {}
-
-#if _LIBCPP_STD_VER <= 14
-template <class _Rp, class... _ArgTypes>
-template <class _Fp, class _Alloc, class>
-function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc& __a,
-                                      _Fp __f)
-    : __f_(_VSTD::move(__f), __a) {}
-#endif
-
-template<class _Rp, class ..._ArgTypes>
-function<_Rp(_ArgTypes...)>&
-function<_Rp(_ArgTypes...)>::operator=(const function& __f)
-{
-    function(__f).swap(*this);
-    return *this;
-}
-
-template<class _Rp, class ..._ArgTypes>
-function<_Rp(_ArgTypes...)>&
-function<_Rp(_ArgTypes...)>::operator=(function&& __f) _NOEXCEPT
-{
-    __f_ = _VSTD::move(__f.__f_);
-    return *this;
-}
-
-template<class _Rp, class ..._ArgTypes>
-function<_Rp(_ArgTypes...)>&
-function<_Rp(_ArgTypes...)>::operator=(nullptr_t) _NOEXCEPT
-{
-    __f_ = nullptr;
-    return *this;
-}
-
-template<class _Rp, class ..._ArgTypes>
-template <class _Fp, class>
-function<_Rp(_ArgTypes...)>&
-function<_Rp(_ArgTypes...)>::operator=(_Fp&& __f)
-{
-    function(_VSTD::forward<_Fp>(__f)).swap(*this);
-    return *this;
-}
-
-template<class _Rp, class ..._ArgTypes>
-function<_Rp(_ArgTypes...)>::~function() {}
-
-template<class _Rp, class ..._ArgTypes>
-void
-function<_Rp(_ArgTypes...)>::swap(function& __f) _NOEXCEPT
-{
-    __f_.swap(__f.__f_);
-}
-
-template<class _Rp, class ..._ArgTypes>
-_Rp
-function<_Rp(_ArgTypes...)>::operator()(_ArgTypes... __arg) const
-{
-    return __f_(_VSTD::forward<_ArgTypes>(__arg)...);
-}
-
-#ifndef _LIBCPP_NO_RTTI
-
-template<class _Rp, class ..._ArgTypes>
-const std::type_info&
-function<_Rp(_ArgTypes...)>::target_type() const _NOEXCEPT
-{
-    return __f_.target_type();
-}
-
-template<class _Rp, class ..._ArgTypes>
-template <typename _Tp>
-_Tp*
-function<_Rp(_ArgTypes...)>::target() _NOEXCEPT
-{
-    return (_Tp*)(__f_.template target<_Tp>());
-}
-
-template<class _Rp, class ..._ArgTypes>
-template <typename _Tp>
-const _Tp*
-function<_Rp(_ArgTypes...)>::target() const _NOEXCEPT
-{
-    return __f_.template target<_Tp>();
-}
-
-#endif // _LIBCPP_NO_RTTI
-
-template <class _Rp, class... _ArgTypes>
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(const function<_Rp(_ArgTypes...)>& __f, nullptr_t) _NOEXCEPT {return !__f;}
-
-template <class _Rp, class... _ArgTypes>
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(nullptr_t, const function<_Rp(_ArgTypes...)>& __f) _NOEXCEPT {return !__f;}
-
-template <class _Rp, class... _ArgTypes>
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator!=(const function<_Rp(_ArgTypes...)>& __f, nullptr_t) _NOEXCEPT {return (bool)__f;}
-
-template <class _Rp, class... _ArgTypes>
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator!=(nullptr_t, const function<_Rp(_ArgTypes...)>& __f) _NOEXCEPT {return (bool)__f;}
-
-template <class _Rp, class... _ArgTypes>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-swap(function<_Rp(_ArgTypes...)>& __x, function<_Rp(_ArgTypes...)>& __y) _NOEXCEPT
-{return __x.swap(__y);}
-
-#else // _LIBCPP_CXX03_LANG
-
-#include <__functional_03>
-
-#endif
-
-////////////////////////////////////////////////////////////////////////////////
-//                                  BIND
-//==============================================================================
-
-template<class _Tp> struct __is_bind_expression : public false_type {};
-template<class _Tp> struct _LIBCPP_TEMPLATE_VIS is_bind_expression
-    : public __is_bind_expression<typename remove_cv<_Tp>::type> {};
-
-#if _LIBCPP_STD_VER > 14
-template <class _Tp>
-_LIBCPP_INLINE_VAR constexpr size_t is_bind_expression_v = is_bind_expression<_Tp>::value;
-#endif
-
-template<class _Tp> struct __is_placeholder : public integral_constant<int, 0> {};
-template<class _Tp> struct _LIBCPP_TEMPLATE_VIS is_placeholder
-    : public __is_placeholder<typename remove_cv<_Tp>::type> {};
-
-#if _LIBCPP_STD_VER > 14
-template <class _Tp>
-_LIBCPP_INLINE_VAR constexpr size_t is_placeholder_v = is_placeholder<_Tp>::value;
-#endif
-
-namespace placeholders
-{
-
-template <int _Np> struct __ph {};
-
-#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
-_LIBCPP_FUNC_VIS extern const __ph<1>   _1;
-_LIBCPP_FUNC_VIS extern const __ph<2>   _2;
-_LIBCPP_FUNC_VIS extern const __ph<3>   _3;
-_LIBCPP_FUNC_VIS extern const __ph<4>   _4;
-_LIBCPP_FUNC_VIS extern const __ph<5>   _5;
-_LIBCPP_FUNC_VIS extern const __ph<6>   _6;
-_LIBCPP_FUNC_VIS extern const __ph<7>   _7;
-_LIBCPP_FUNC_VIS extern const __ph<8>   _8;
-_LIBCPP_FUNC_VIS extern const __ph<9>   _9;
-_LIBCPP_FUNC_VIS extern const __ph<10> _10;
-#else
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<1>   _1{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<2>   _2{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<3>   _3{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<4>   _4{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<5>   _5{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<6>   _6{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<7>   _7{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<8>   _8{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<9>   _9{};
-/* _LIBCPP_INLINE_VAR */ constexpr __ph<10> _10{};
-#endif // defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
-
-}  // placeholders
-
-template<int _Np>
-struct __is_placeholder<placeholders::__ph<_Np> >
-    : public integral_constant<int, _Np> {};
-
-
-#ifndef _LIBCPP_CXX03_LANG
-
-template <class _Tp, class _Uj>
-inline _LIBCPP_INLINE_VISIBILITY
-_Tp&
-__mu(reference_wrapper<_Tp> __t, _Uj&)
-{
-    return __t.get();
-}
-
-template <class _Ti, class ..._Uj, size_t ..._Indx>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __invoke_of<_Ti&, _Uj...>::type
-__mu_expand(_Ti& __ti, tuple<_Uj...>& __uj, __tuple_indices<_Indx...>)
-{
-    return __ti(_VSTD::forward<_Uj>(_VSTD::get<_Indx>(__uj))...);
-}
-
-template <class _Ti, class ..._Uj>
-inline _LIBCPP_INLINE_VISIBILITY
-typename _EnableIf
-<
-    is_bind_expression<_Ti>::value,
-    __invoke_of<_Ti&, _Uj...>
->::type
-__mu(_Ti& __ti, tuple<_Uj...>& __uj)
-{
-    typedef typename __make_tuple_indices<sizeof...(_Uj)>::type __indices;
-    return _VSTD::__mu_expand(__ti, __uj, __indices());
-}
-
-template <bool IsPh, class _Ti, class _Uj>
-struct __mu_return2 {};
-
-template <class _Ti, class _Uj>
-struct __mu_return2<true, _Ti, _Uj>
-{
-    typedef typename tuple_element<is_placeholder<_Ti>::value - 1, _Uj>::type type;
-};
-
-template <class _Ti, class _Uj>
-inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
-    0 < is_placeholder<_Ti>::value,
-    typename __mu_return2<0 < is_placeholder<_Ti>::value, _Ti, _Uj>::type
->::type
-__mu(_Ti&, _Uj& __uj)
-{
-    const size_t _Indx = is_placeholder<_Ti>::value - 1;
-    return _VSTD::forward<typename tuple_element<_Indx, _Uj>::type>(_VSTD::get<_Indx>(__uj));
-}
-
-template <class _Ti, class _Uj>
-inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
-    !is_bind_expression<_Ti>::value &&
-    is_placeholder<_Ti>::value == 0 &&
-    !__is_reference_wrapper<_Ti>::value,
-    _Ti&
->::type
-__mu(_Ti& __ti, _Uj&)
-{
-    return __ti;
-}
-
-template <class _Ti, bool IsReferenceWrapper, bool IsBindEx, bool IsPh,
-          class _TupleUj>
-struct __mu_return_impl;
-
-template <bool _Invokable, class _Ti, class ..._Uj>
-struct __mu_return_invokable  // false
-{
-    typedef __nat type;
-};
-
-template <class _Ti, class ..._Uj>
-struct __mu_return_invokable<true, _Ti, _Uj...>
-{
-    typedef typename __invoke_of<_Ti&, _Uj...>::type type;
-};
-
-template <class _Ti, class ..._Uj>
-struct __mu_return_impl<_Ti, false, true, false, tuple<_Uj...> >
-    : public __mu_return_invokable<__invokable<_Ti&, _Uj...>::value, _Ti, _Uj...>
-{
-};
-
-template <class _Ti, class _TupleUj>
-struct __mu_return_impl<_Ti, false, false, true, _TupleUj>
-{
-    typedef typename tuple_element<is_placeholder<_Ti>::value - 1,
-                                   _TupleUj>::type&& type;
-};
-
-template <class _Ti, class _TupleUj>
-struct __mu_return_impl<_Ti, true, false, false, _TupleUj>
-{
-    typedef typename _Ti::type& type;
-};
-
-template <class _Ti, class _TupleUj>
-struct __mu_return_impl<_Ti, false, false, false, _TupleUj>
-{
-    typedef _Ti& type;
-};
-
-template <class _Ti, class _TupleUj>
-struct __mu_return
-    : public __mu_return_impl<_Ti,
-                              __is_reference_wrapper<_Ti>::value,
-                              is_bind_expression<_Ti>::value,
-                              0 < is_placeholder<_Ti>::value &&
-                              is_placeholder<_Ti>::value <= tuple_size<_TupleUj>::value,
-                              _TupleUj>
-{
-};
-
-template <class _Fp, class _BoundArgs, class _TupleUj>
-struct __is_valid_bind_return
-{
-    static const bool value = false;
-};
-
-template <class _Fp, class ..._BoundArgs, class _TupleUj>
-struct __is_valid_bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj>
-{
-    static const bool value = __invokable<_Fp,
-                    typename __mu_return<_BoundArgs, _TupleUj>::type...>::value;
-};
-
-template <class _Fp, class ..._BoundArgs, class _TupleUj>
-struct __is_valid_bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj>
-{
-    static const bool value = __invokable<_Fp,
-                    typename __mu_return<const _BoundArgs, _TupleUj>::type...>::value;
-};
-
-template <class _Fp, class _BoundArgs, class _TupleUj,
-          bool = __is_valid_bind_return<_Fp, _BoundArgs, _TupleUj>::value>
-struct __bind_return;
-
-template <class _Fp, class ..._BoundArgs, class _TupleUj>
-struct __bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj, true>
-{
-    typedef typename __invoke_of
-    <
-        _Fp&,
-        typename __mu_return
-        <
-            _BoundArgs,
-            _TupleUj
-        >::type...
-    >::type type;
-};
-
-template <class _Fp, class ..._BoundArgs, class _TupleUj>
-struct __bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj, true>
-{
-    typedef typename __invoke_of
-    <
-        _Fp&,
-        typename __mu_return
-        <
-            const _BoundArgs,
-            _TupleUj
-        >::type...
-    >::type type;
-};
-
-template <class _Fp, class _BoundArgs, size_t ..._Indx, class _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-typename __bind_return<_Fp, _BoundArgs, _Args>::type
-__apply_functor(_Fp& __f, _BoundArgs& __bound_args, __tuple_indices<_Indx...>,
-                _Args&& __args)
-{
-    return _VSTD::__invoke(__f, _VSTD::__mu(_VSTD::get<_Indx>(__bound_args), __args)...);
-}
-
-template<class _Fp, class ..._BoundArgs>
-class __bind
-#if _LIBCPP_STD_VER <= 17 || !defined(_LIBCPP_ABI_NO_BINDER_BASES)
-    : public __weak_result_type<typename decay<_Fp>::type>
-#endif
-{
-protected:
-    typedef typename decay<_Fp>::type _Fd;
-    typedef tuple<typename decay<_BoundArgs>::type...> _Td;
-private:
-    _Fd __f_;
-    _Td __bound_args_;
-
-    typedef typename __make_tuple_indices<sizeof...(_BoundArgs)>::type __indices;
-public:
-    template <class _Gp, class ..._BA,
-              class = typename enable_if
-                               <
-                                  is_constructible<_Fd, _Gp>::value &&
-                                  !is_same<typename remove_reference<_Gp>::type,
-                                           __bind>::value
-                               >::type>
-      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-      explicit __bind(_Gp&& __f, _BA&& ...__bound_args)
-        : __f_(_VSTD::forward<_Gp>(__f)),
-          __bound_args_(_VSTD::forward<_BA>(__bound_args)...) {}
-
-    template <class ..._Args>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type
-        operator()(_Args&& ...__args)
-        {
-            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
-                                  tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
-        }
-
-    template <class ..._Args>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type
-        operator()(_Args&& ...__args) const
-        {
-            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
-                                   tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
-        }
-};
-
-template<class _Fp, class ..._BoundArgs>
-struct __is_bind_expression<__bind<_Fp, _BoundArgs...> > : public true_type {};
-
-template<class _Rp, class _Fp, class ..._BoundArgs>
-class __bind_r
-    : public __bind<_Fp, _BoundArgs...>
-{
-    typedef __bind<_Fp, _BoundArgs...> base;
-    typedef typename base::_Fd _Fd;
-    typedef typename base::_Td _Td;
-public:
-    typedef _Rp result_type;
-
-
-    template <class _Gp, class ..._BA,
-              class = typename enable_if
-                               <
-                                  is_constructible<_Fd, _Gp>::value &&
-                                  !is_same<typename remove_reference<_Gp>::type,
-                                           __bind_r>::value
-                               >::type>
-      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-      explicit __bind_r(_Gp&& __f, _BA&& ...__bound_args)
-        : base(_VSTD::forward<_Gp>(__f),
-               _VSTD::forward<_BA>(__bound_args)...) {}
-
-    template <class ..._Args>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        typename enable_if
-        <
-            is_convertible<typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type,
-                           result_type>::value || is_void<_Rp>::value,
-            result_type
-        >::type
-        operator()(_Args&& ...__args)
-        {
-            typedef __invoke_void_return_wrapper<_Rp> _Invoker;
-            return _Invoker::__call(static_cast<base&>(*this), _VSTD::forward<_Args>(__args)...);
-        }
-
-    template <class ..._Args>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        typename enable_if
-        <
-            is_convertible<typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type,
-                           result_type>::value || is_void<_Rp>::value,
-            result_type
-        >::type
-        operator()(_Args&& ...__args) const
-        {
-            typedef __invoke_void_return_wrapper<_Rp> _Invoker;
-            return _Invoker::__call(static_cast<base const&>(*this), _VSTD::forward<_Args>(__args)...);
-        }
-};
-
-template<class _Rp, class _Fp, class ..._BoundArgs>
-struct __is_bind_expression<__bind_r<_Rp, _Fp, _BoundArgs...> > : public true_type {};
-
-template<class _Fp, class ..._BoundArgs>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-__bind<_Fp, _BoundArgs...>
-bind(_Fp&& __f, _BoundArgs&&... __bound_args)
-{
-    typedef __bind<_Fp, _BoundArgs...> type;
-    return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
-}
-
-template<class _Rp, class _Fp, class ..._BoundArgs>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-__bind_r<_Rp, _Fp, _BoundArgs...>
-bind(_Fp&& __f, _BoundArgs&&... __bound_args)
-{
-    typedef __bind_r<_Rp, _Fp, _BoundArgs...> type;
-    return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
-}
-
-#endif // _LIBCPP_CXX03_LANG
-
-#if _LIBCPP_STD_VER > 14
-
-template<class _Op, class _Tuple,
-         class _Idxs = typename __make_tuple_indices<tuple_size<_Tuple>::value>::type>
-struct __perfect_forward_impl;
-
-template<class _Op, class... _Bound, size_t... _Idxs>
-struct __perfect_forward_impl<_Op, __tuple_types<_Bound...>, __tuple_indices<_Idxs...>>
-{
-    tuple<_Bound...> __bound_;
-
-    template<class... _Args>
-    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) &
-    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...)))
-    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...))
-    {return           _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...);}
-
-    template<class... _Args>
-    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) const&
-    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...)))
-    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...))
-    {return           _Op::__call(_VSTD::get<_Idxs>(__bound_)..., _VSTD::forward<_Args>(__args)...);}
-
-    template<class... _Args>
-    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) &&
-    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
-                                  _VSTD::forward<_Args>(__args)...)))
-    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
-                                  _VSTD::forward<_Args>(__args)...))
-    {return           _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
-                                  _VSTD::forward<_Args>(__args)...);}
-
-    template<class... _Args>
-    _LIBCPP_INLINE_VISIBILITY constexpr auto operator()(_Args&&... __args) const&&
-    noexcept(noexcept(_Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
-                                  _VSTD::forward<_Args>(__args)...)))
-    -> decltype(      _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
-                                  _VSTD::forward<_Args>(__args)...))
-    {return           _Op::__call(_VSTD::get<_Idxs>(_VSTD::move(__bound_))...,
-                                  _VSTD::forward<_Args>(__args)...);}
-
-    template<class _Fn = typename tuple_element<0, tuple<_Bound...>>::type,
-             class = _EnableIf<is_copy_constructible_v<_Fn>>>
-    constexpr __perfect_forward_impl(__perfect_forward_impl const& __other)
-        : __bound_(__other.__bound_) {}
-
-    template<class _Fn = typename tuple_element<0, tuple<_Bound...>>::type,
-             class = _EnableIf<is_move_constructible_v<_Fn>>>
-    constexpr __perfect_forward_impl(__perfect_forward_impl && __other)
-        : __bound_(_VSTD::move(__other.__bound_)) {}
-
-    template<class... _BoundArgs>
-    explicit constexpr __perfect_forward_impl(_BoundArgs&&... __bound) :
-        __bound_(_VSTD::forward<_BoundArgs>(__bound)...) { }
-};
-
-template<class _Op, class... _Args>
-using __perfect_forward =
-    __perfect_forward_impl<_Op, __tuple_types<decay_t<_Args>...>>;
-
-struct __not_fn_op
-{
-    template<class... _Args>
-    static _LIBCPP_CONSTEXPR_AFTER_CXX17 auto __call(_Args&&... __args)
-    noexcept(noexcept(!_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
-    -> decltype(      !_VSTD::invoke(_VSTD::forward<_Args>(__args)...))
-    { return          !_VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
-};
-
-template<class _Fn,
-         class = _EnableIf<is_constructible_v<decay_t<_Fn>, _Fn> &&
-                           is_move_constructible_v<_Fn>>>
-_LIBCPP_CONSTEXPR_AFTER_CXX17 auto not_fn(_Fn&& __f)
-{
-    return __perfect_forward<__not_fn_op, _Fn>(_VSTD::forward<_Fn>(__f));
-}
-
-#endif // _LIBCPP_STD_VER > 14
-
-#if _LIBCPP_STD_VER > 17
-
-struct __bind_front_op
-{
-    template<class... _Args>
-    constexpr static auto __call(_Args&&... __args)
-    noexcept(noexcept(_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
-    -> decltype(      _VSTD::invoke(_VSTD::forward<_Args>(__args)...))
-    { return          _VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
-};
-
-template<class _Fn, class... _Args,
-         class = _EnableIf<conjunction<is_constructible<decay_t<_Fn>, _Fn>,
-                                       is_move_constructible<decay_t<_Fn>>,
-                                       is_constructible<decay_t<_Args>, _Args>...,
-                                       is_move_constructible<decay_t<_Args>>...
-                                       >::value>>
-constexpr auto bind_front(_Fn&& __f, _Args&&... __args)
-{
-    return __perfect_forward<__bind_front_op, _Fn, _Args...>(_VSTD::forward<_Fn>(__f),
-                                                             _VSTD::forward<_Args>(__args)...);
-}
-
-#endif // _LIBCPP_STD_VER > 17
-
-// struct hash<T*> in <memory>
-
-#if _LIBCPP_STD_VER > 14
-
-// default searcher
-template<class _ForwardIterator, class _BinaryPredicate = equal_to<>>
-class _LIBCPP_TEMPLATE_VIS default_searcher {
-public:
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    default_searcher(_ForwardIterator __f, _ForwardIterator __l,
-                       _BinaryPredicate __p = _BinaryPredicate())
-        : __first_(__f), __last_(__l), __pred_(__p) {}
-
-    template <typename _ForwardIterator2>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    pair<_ForwardIterator2, _ForwardIterator2>
-    operator () (_ForwardIterator2 __f, _ForwardIterator2 __l) const
-    {
-        return _VSTD::__search(__f, __l, __first_, __last_, __pred_,
-            typename iterator_traits<_ForwardIterator>::iterator_category(),
-            typename iterator_traits<_ForwardIterator2>::iterator_category());
-    }
-
-private:
-    _ForwardIterator __first_;
-    _ForwardIterator __last_;
-    _BinaryPredicate __pred_;
-    };
-
-#endif // _LIBCPP_STD_VER > 14
-
-#if _LIBCPP_STD_VER > 17
-template <class _Tp>
-using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
-
-template <class _Tp>
-using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
-#endif // > C++17
-
-#if _LIBCPP_STD_VER > 17
-// [func.identity]
-struct identity {
-    template<class _Tp>
-    _LIBCPP_NODISCARD_EXT constexpr _Tp&& operator()(_Tp&& __t) const noexcept
-    {
-        return _VSTD::forward<_Tp>(__t);
-    }
-
-    using is_transparent = void;
-};
-#endif // _LIBCPP_STD_VER > 17
-
-#if !defined(_LIBCPP_HAS_NO_RANGES)
-
-namespace ranges {
-
-struct equal_to {
-  template <class _Tp, class _Up>
-  requires equality_comparable_with<_Tp, _Up>
-  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
-      noexcept(noexcept(bool(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u)))) {
-    return _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u);
-  }
-
-  using is_transparent = void;
-};
-
-struct not_equal_to {
-  template <class _Tp, class _Up>
-  requires equality_comparable_with<_Tp, _Up>
-  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
-      noexcept(noexcept(bool(!(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u))))) {
-    return !(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u));
-  }
-
-  using is_transparent = void;
-};
-
-struct greater {
-  template <class _Tp, class _Up>
-  requires totally_ordered_with<_Tp, _Up>
-  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
-      noexcept(noexcept(bool(_VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t)))) {
-    return _VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t);
-  }
-
-  using is_transparent = void;
-};
-
-struct less {
-  template <class _Tp, class _Up>
-  requires totally_ordered_with<_Tp, _Up>
-  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
-      noexcept(noexcept(bool(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u)))) {
-    return _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u);
-  }
-
-  using is_transparent = void;
-};
-
-struct greater_equal {
-  template <class _Tp, class _Up>
-  requires totally_ordered_with<_Tp, _Up>
-  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
-      noexcept(noexcept(bool(!(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u))))) {
-    return !(_VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u));
-  }
-
-  using is_transparent = void;
-};
-
-struct less_equal {
-  template <class _Tp, class _Up>
-  requires totally_ordered_with<_Tp, _Up>
-  [[nodiscard]] constexpr bool operator()(_Tp &&__t, _Up &&__u) const
-      noexcept(noexcept(bool(!(_VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t))))) {
-    return !(_VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t));
-  }
-
-  using is_transparent = void;
-};
-
-} // namespace ranges
-
-#endif // !defined(_LIBCPP_HAS_NO_RANGES)
-
-_LIBCPP_END_NAMESPACE_STD
-
 #endif // _LIBCPP_FUNCTIONAL

libcxx/include/future

 
 }  // std
 
 */
 
 #include <__availability>
 #include <__config>
 #include <__debug>
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
 #include <__utility/__decay_copy.h>
 #include <__utility/forward.h>
 #include <chrono>
 #include <exception>
 #include <memory>
 #include <mutex>
 #include <system_error>
 #include <thread>

libcxx/include/map

 erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);  // C++20
 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
+#include <__functional/is_transparent.h>
 #include <__node_handle>
 #include <__tree>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <memory>

libcxx/include/memory

 
 */
 
 #include <__config>
 #include <__functional_base>
 #include <__memory/addressof.h>
 #include <__memory/allocation_guard.h>
 #include <__memory/allocator.h>
+#include <__memory/allocator_arg_t.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/compressed_pair.h>
 #include <__memory/construct_at.h>
 #include <__memory/pointer_safety.h>
 #include <__memory/pointer_traits.h>
 #include <__memory/raw_storage_iterator.h>
 #include <__memory/shared_ptr.h>
 #include <__memory/temporary_buffer.h>
 #include <__memory/uninitialized_algorithms.h>
 #include <__memory/unique_ptr.h>
+#include <__memory/uses_allocator.h>
 #include <compare>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
 #include <iosfwd>
 #include <iterator>
 #include <new>
 #include <stdexcept>

libcxx/include/module.modulemap

module std [system] {
   }
   module fstream {
     header "fstream"
     export *
   }
   module functional {
     header "functional"
     export *
+
     module __functional {
-      module hash           { header "__functional/hash.h"           }
-      module unary_function { header "__functional/unary_function.h" }
-      module unwrap_ref     { header "__functional/unwrap_ref.h"     }
+      module binary_function            { header "__functional/binary_function.h" }
+      module binary_negate              { header "__functional/binary_negate.h" }
+      module bind                       { header "__functional/bind.h" }
+      module binder1st                  { header "__functional/binder1st.h" }
+      module binder2nd                  { header "__functional/binder2nd.h" }
+      module bind_front                 { header "__functional/bind_front.h" }
+      module bit_and                    { header "__functional/bit_and.h" }
+      module bit_not                    { header "__functional/bit_not.h" }
+      module bit_or                     { header "__functional/bit_or.h" }
+      module bit_xor                    { header "__functional/bit_xor.h" }
+      module default_searcher           { header "__functional/default_searcher.h" }
+      module divides                    { header "__functional/divides.h" }
+      module equal_to                   { header "__functional/equal_to.h" }
+      module function                   { header "__functional/function.h" }
+      module greater_equal              { header "__functional/greater_equal.h" }
+      module greater                    { header "__functional/greater.h" }
+      module hash                       { header "__functional/hash.h" }
+      module identity                   { header "__functional/identity.h" }
+      module invoke                     { header "__functional/invoke.h" }
+      module less_equal                 { header "__functional/less_equal.h" }
+      module less                       { header "__functional/less.h" }
+      module logical_and                { header "__functional/logical_and.h" }
+      module logical_not                { header "__functional/logical_not.h" }
+      module logical_or                 { header "__functional/logical_or.h" }
+      module mem_fn                     { header "__functional/mem_fn.h"  }
+      module mem_fun_ref                { header "__functional/mem_fun_ref.h"  }
+      module minus                      { header "__functional/minus.h" }
+      module modulus                    { header "__functional/modulus.h" }
+      module multiplies                 { header "__functional/multiplies.h" }
+      module negate                     { header "__functional/negate.h" }
+      module not_equal_to               { header "__functional/not_equal_to.h" }
+      module not_fn                     { header "__functional/not_fn.h" }
+      module perfect_forward            { header "__functional/perfect_forward.h" }
+      module plus                       { header "__functional/plus.h" }
+      module pointer_to_binary_function { header "__functional/pointer_to_binary_function.h" }
+      module pointer_to_unary_function  { header "__functional/pointer_to_unary_function.h" }
+      module reference_wrapper          { header "__functional/reference_wrapper.h" }
+      module unary_function             { header "__functional/unary_function.h" }
+      module unary_negate               { header "__functional/unary_negate.h" }
+      module unwrap_ref                 { header "__functional/unwrap_ref.h" }
+      module weak_result_type           { header "__functional/weak_result_type.h" }
+
+      module ranges {
+        module equal_to      { header "__functional/ranges/equal_to.h"      }
+        module greater_equal { header "__functional/ranges/greater_equal.h" }
+        module greater       { header "__functional/ranges/greater.h"       }
+        module less_equal    { header "__functional/ranges/less_equal.h"    }
+        module less          { header "__functional/ranges/less.h"          }
+        module not_equal_to  { header "__functional/ranges/not_equal_to.h"  }
+      }
     }
   }
   module future {
     header "future"
     export *
   }
   module initializer_list {
     header "initializer_list"
     export *
module std [system] {
   module memory {
     header "memory"
     export *
 
     module __memory {
       module addressof                { header "__memory/addressof.h"                }
       module allocation_guard         { header "__memory/allocation_guard.h"         }
       module allocator_traits         { header "__memory/allocator_traits.h"         }
+      module allocator_arg_t          { header "__memory/allocator_arg_t.h"          }
       module allocator                { header "__memory/allocator.h"                }
       module auto_ptr                 { header "__memory/auto_ptr.h"                 }
       module compressed_pair          { header "__memory/compressed_pair.h"          }
       module construct_at             { header "__memory/construct_at.h"             }
       module pointer_safety           { header "__memory/pointer_safety.h"           }
       module pointer_traits           { header "__memory/pointer_traits.h"           }
       module raw_storage_iterator     { header "__memory/raw_storage_iterator.h"     }
       module shared_ptr               { header "__memory/shared_ptr.h"               }
module std [system] {
   // libcpp_version not modularised since it's just a version number
   // FIXME: These should be private.
   module __availability      { header "__availability"      export * }
   module __bit_reference     { header "__bit_reference"     export * }
   module __bits              { header "__bits"              export * }
   module __debug             { header "__debug"             export * }
   module __errc              { header "__errc"              export * }
   module __function_like     { header "__function_like.h"   export * }
-  module __functional_base   { header "__functional_base"   export * }
   module __hash_table        { header "__hash_table"        export * }
   module __locale            { header "__locale"            export * }
   module __mutex_base        { header "__mutex_base"        export * }
   module __node_handle       { header "__node_handle"       export * }
   module __nullptr           { header "__nullptr"           export * }
   module __split_buffer      { header "__split_buffer"      export * }
   module __std_stream        { header "__std_stream"        export * }
   module __string            { header "__string"            export * }

libcxx/include/queue

void swap(priority_queue<T, Container, Compare>& x,
             priority_queue<T, Container, Compare>& y)
             noexcept(noexcept(x.swap(y)));
 
 }  // std
 
 */
 
 #include <__config>
+#include <__memory/uses_allocator.h>
 #include <__utility/forward.h>
 #include <algorithm>
 #include <compare>
 #include <deque>
 #include <functional>
 #include <vector>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)

libcxx/include/set

 erase_if(multiset<Key, Compare, Allocator>& c, Predicate pred);  // C++20
 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
+#include <__functional/is_transparent.h>
 #include <__node_handle>
 #include <__tree>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <version>

libcxx/include/stack

template <class T, class Container>
   void swap(stack<T, Container>& x, stack<T, Container>& y)
   noexcept(noexcept(x.swap(y)));
 
 }  // std
 
 */
 
 #include <__config>
+#include <__memory/uses_allocator.h>
 #include <__utility/forward.h>
 #include <deque>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

libcxx/include/system_error

 template <> struct hash<std::error_condition>;
 
 }  // std
 
 */
 
 #include <__config>
 #include <__errc>
-#include <__functional_base> // unary_function
+#include <__functional/unary_function.h>
+#include <__functional_base>
 #include <compare>
 #include <stdexcept>
 #include <string>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif

libcxx/include/tuple

template <class... Types>
   void
   swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(noexcept(x.swap(y)));
 
 }  // std
 
 */
 
 #include <__config>
-#include <__functional_base>
 #include <__functional/unwrap_ref.h>
+#include <__functional_base>
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
+#include <__tuple>
 #include <__utility/forward.h>
 #include <__utility/move.h>
-#include <__tuple>
 #include <compare>
 #include <cstddef>
 #include <type_traits>
 #include <utility>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header

libcxx/include/typeindex

struct hash<type_index>
     size_t operator()(type_index index) const noexcept;
 };
 
 }  // std
 
 */
 
 #include <__config>
+#include <__functional/unary_function.h>
 #include <__functional_base>
 #include <compare>
 #include <typeinfo>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 

libcxx/include/unordered_map

operator!=(const unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
                const unordered_multimap<Key, T, Hash, Pred, Alloc>& y);
 
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
+#include <__functional/is_transparent.h>
 #include <__hash_table>
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <iterator> // __libcpp_erase_if_container
 #include <stdexcept>
 #include <tuple>

libcxx/include/unordered_set

template <class Value, class Hash, class Pred, class Alloc>
     operator!=(const unordered_multiset<Value, Hash, Pred, Alloc>& x,
                const unordered_multiset<Value, Hash, Pred, Alloc>& y);
 }  // std
 
 */
 
 #include <__config>
 #include <__debug>
+#include <__functional/is_transparent.h>
 #include <__hash_table>
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
 #include <functional>
 #include <iterator> // __libcpp_erase_if_container
 #include <version>
 

libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/result_of.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // <functional>
 
 // result_of<Fn(ArgTypes...)>
 
 #include <type_traits>
-#include <memory>
 #include <cassert>
+#include <functional>
+#include <memory>
 #include "test_macros.h"
 
 struct S
 {
     typedef short (*FreeFunc)(long);
     operator FreeFunc() const;
     double operator()(char, int&);
     double const& operator()(char, int&) const;

libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/result_of11.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // UNSUPPORTED: c++03
 //
 // <functional>
 //
 // result_of<Fn(ArgTypes...)>
 
 #include <type_traits>
+#include <functional>
 #include <memory>
 #include <utility>
 #include "test_macros.h"
 
 // Ignore warnings about volatile in parameters being deprecated.
 // We know it is, but we still have to test it.
 #if defined(__GNUC__) && (__GNUC__ >= 10) && !defined(__clang__)
 #   pragma GCC diagnostic ignored "-Wvolatile"

libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/deduct.pass.cpp

 
 // <tuple>
 
 // Test that the constructors offered by std::tuple are formulated
 // so they're compatible with implicit deduction guides, or if that's not
 // possible that they provide explicit guides to make it work.
 
 #include <tuple>
-#include <memory>
 #include <cassert>
+#include <functional>
+#include <memory>
 
 #include "test_macros.h"
 #include "archetypes.h"
 
 
 // Overloads
 //  using A = Allocator
 //  using AT = std::allocator_arg_t