[ADT] Add an llvm::erase_if utility to make the standard erase+remove_if pattern easier to write.

[chandlerc]

Summary

What it says on the tin...

[aaron.ballman]

LGTM!

include/llvm/ADT/STLExtras.h

819

Typo: colon instead of semi-colon?

include/llvm/ADT/STLExtras.h

 
 /// Provide wrappers to std::partition which take ranges instead of having to
 /// pass begin/end explicitly.
 template <typename R, typename UnaryPredicate>
 auto partition(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range)) {
   return std::partition(std::begin(Range), std::end(Range), P);
 }
 
+/// Provide a container algorithm similar to C++ Library Fundamentals v2's
+/// `erase_if` which is equivalent to;
+///
+///   C.erase(remove_if(C, pred), C.end());
+///
+/// This version works for any container with an erase method call accepting
+/// two iterators.
+template <typename Container, typename UnaryPredicate>
+void erase_if(Container &C, UnaryPredicate P) {
+  C.erase(remove_if(C, P), C.end());
+}
+
 //===----------------------------------------------------------------------===//
 //     Extra additions to <memory>
 //===----------------------------------------------------------------------===//
 
 // Implement make_unique according to N3656.
 
 /// \brief Constructs a `new T()` with the given args and returns a
 ///        `unique_ptr<T>` which owns the object.

unittests/ADT/STLExtrasTest.cpp

TEST(STLExtrasTest, PartitionAdaptor) {
   EXPECT_EQ(6, V[2]);
   EXPECT_EQ(8, V[3]);
   EXPECT_EQ(1, V[4]);
   EXPECT_EQ(3, V[5]);
   EXPECT_EQ(5, V[6]);
   EXPECT_EQ(7, V[7]);
 }
 
+TEST(STLExtrasTest, EraseIf) {
+  std::vector<int> V = {1, 2, 3, 4, 5, 6, 7, 8};
+
+  erase_if(V, [](int i) { return i % 2 == 0; });
+  EXPECT_EQ(4u, V.size());
+  EXPECT_EQ(1, V[0]);
+  EXPECT_EQ(3, V[1]);
+  EXPECT_EQ(5, V[2]);
+  EXPECT_EQ(7, V[3]);
+}
+
 }