[libc++][spaceship] P1614R2: Added `operator==` to `slice`

[H-G-Hristov]

Summary

Implements parts of P1614R2:

• Added operator== to slice

[H-G-Hristov]

Added synopsis

[Mordante]

Thanks for working on this! I would like to land D152297 first for this one too. But this needs some addition work.

libcxx/include/valarray

410

Note this function should be a hidden friend per http://eel.is/c++draft/hidden.friends.

libcxx/test/std/numerics/numarray/class.slice/slice.ops/slice.ops.pass.cpp

19

Why not use the normal test macros instead?

[H-G-Hristov]

Try to fix CI

[H-G-Hristov]

Addressed comments

[Mordante]

LGTM!

libcxx/docs/Status/SpaceshipProjects.csv

 | `[range.split.inner] <https://wg21.link/range.split.inner>`_,| remove ops `split_view::inner_iterator`,None,Unassigned,|Not Started|
 - `5.10 Clause 25: Algorithms library <https://wg21.link/p1614r2#clause-25-algorithms-library>`_,,,,
 "| `[algorithm.syn] <https://wg21.link/algorithm.syn>`_
 | `[alg.three.way] <https://wg21.link/alg.three.way>`_",| `lexicographical_compare_three_way <https://reviews.llvm.org/D131395>`_,[comparisons.three.way],Adrian Vogelsgesang,|Complete|
 - `5.11 Clause 26: Numerics library <https://wg21.link/p1614r2#clause-26-numerics-library>`_,,,,
 "| `[complex.syn] <https://wg21.link/complex.syn>`_
 | `[complex.ops] <https://wg21.link/complex.ops>`_",| remove ops `complex <https://reviews.llvm.org/D152615>`_,None,Hristo Hristov,|In Progress|
 "| `[class.slice.overview] <https://wg21.link/class.slice.overview>`_
-| `[slice.ops] <https://wg21.link/slice.ops>`_",| `slice <https://reviews.llvm.org/D152617>`_,None,Hristo Hristov,|In Progress|
+| `[slice.ops] <https://wg21.link/slice.ops>`_",| `slice <https://reviews.llvm.org/D152617>`_,None,Hristo Hristov,|Complete|
 - `5.12 Clause 27: Time library <https://wg21.link/p1614r2#clause-27-time-library>`_,,,,
 | `[time.syn] <https://wg21.link/time.syn>`_,|,None,Unassigned,|Not Started|
 | `[time.duration.comparisons] <https://wg21.link/time.duration.comparisons>`_, `chrono::duration <https://reviews.llvm.org/D145881>`_, None, Hristo Hristov, |Complete|
 | `[time.point.comparisons] <https://wg21.link/time.point.comparisons>`_, `chrono::time_point <https://reviews.llvm.org/D146250>`_, None, Hristo Hristov, |Complete|
 "| `[time.cal.day.nonmembers] <https://wg21.link/time.cal.day.nonmembers>`_
 | `[time.cal.month.nonmembers] <https://wg21.link/time.cal.month.nonmembers>`_
 | `[time.cal.year.nonmembers] <https://wg21.link/time.cal.year.nonmembers>`_
 | `[time.cal.md.nonmembers] <https://wg21.link/time.cal.md.nonmembers>`_

libcxx/include/valarray

 {
 public:
     slice();
     slice(size_t start, size_t size, size_t stride);
 
     size_t start()  const;
     size_t size()   const;
     size_t stride() const;
+
+    friend bool operator==(const slice& x, const slice& y); // since C++20
 };
 
 template <class T>
 class slice_array
 {
 public:
     typedef T value_type;
 
slice(size_t __start, size_t __size, size_t __stride)
         : __start_(__start),
           __size_(__size),
           __stride_(__stride)
           {}
 
     _LIBCPP_INLINE_VISIBILITY size_t start()  const {return __start_;}
     _LIBCPP_INLINE_VISIBILITY size_t size()   const {return __size_;}
     _LIBCPP_INLINE_VISIBILITY size_t stride() const {return __stride_;}
+
+#if _LIBCPP_STD_VER >= 20
+
+    _LIBCPP_HIDE_FROM_ABI friend bool operator==(const slice& __x, const slice& __y) {
+      return __x.start() == __y.start() && __x.size() == __y.size() && __x.stride() == __y.stride();
+    }
+
+#endif
 };
 
 template <class _Tp> class _LIBCPP_TEMPLATE_VIS slice_array;
 class _LIBCPP_TYPE_VIS gslice;
 template <class _Tp> class _LIBCPP_TEMPLATE_VIS gslice_array;
 template <class _Tp> class _LIBCPP_TEMPLATE_VIS mask_array;
 template <class _Tp> class _LIBCPP_TEMPLATE_VIS indirect_array;
 

libcxx/test/std/numerics/numarray/class.slice/slice.ops/slice.ops.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, c++11, c++14, c++17
+
+// <valarray>
+
+// class slice;
+
+// friend bool operator==(const slice& x, const slice& y);
+
+#include <cassert>
+#include <valarray>
+
+#include "test_comparisons.h"
+
+void test() {
+  {
+    std::slice s1;
+    std::slice s2;
+
+    assert(testEquality(s1, s2, true));
+  }
+  {
+    std::slice s1{1, 2, 3};
+    std::slice s2{1, 2, 3};
+
+    assert(testEquality(s1, s2, true));
+  }
+  {
+    std::slice s1;
+    std::slice s2{1, 2, 3};
+
+    assert(testEquality(s1, s2, false));
+  }
+  {
+    std::slice s1{0, 2, 3};
+    std::slice s2{1, 2, 3};
+
+    assert(testEquality(s1, s2, false));
+  }
+  {
+    std::slice s1{1, 0, 3};
+    std::slice s2{1, 2, 3};
+
+    assert(testEquality(s1, s2, false));
+  }
+  {
+    std::slice s1{1, 2, 0};
+    std::slice s2{1, 2, 3};
+
+    assert(testEquality(s1, s2, false));
+  }
+}
+
+int main(int, char**) {
+  test();
+
+  return 0;
+}