Implement P1209 - Adopt Consistent Container Erasure from Library Fundamentals 2 for C++20. Reviewed as https://reviews.llvm.org/D55532

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@349178 91177308-0d34-0410-b5e6-96231b3b80d8

include/functional

@@ -2953,6 +2953,18 @@ template <class _Tp>
 using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
 #endif // > C++17
 
+template <class _Container, class _Predicate>
+inline void __libcpp_erase_if_container( _Container& __c, _Predicate __pred)
+{
+	for (typename _Container::iterator __iter = __c.begin(), __last = __c.end(); __iter != __last;)
+	{
+		if (__pred(*__iter))
+			__iter = __c.erase(__iter);
+		else
+			++__iter;
+	}
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_FUNCTIONAL