1// -*- C++ -*-
 2//===----------------------------------------------------------------------===//
 3//
 4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 5// See https://llvm.org/LICENSE.txt for license information.
 6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 7//
 8//===----------------------------------------------------------------------===//
 9
10#ifndef _LIBCPP___ITERATOR_MERGEABLE_H
11#define _LIBCPP___ITERATOR_MERGEABLE_H
12
13#include <__config>
14#include <__functional/identity.h>
15#include <__functional/ranges_operations.h>
16#include <__iterator/concepts.h>
17#include <__iterator/projected.h>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20#  pragma GCC system_header
21#endif
22
23_LIBCPP_BEGIN_NAMESPACE_STD
24
25#if _LIBCPP_STD_VER >= 20
26
27template <class _Input1,
28          class _Input2,
29          class _Output,
30          class _Comp  = ranges::less,
31          class _Proj1 = identity,
32          class _Proj2 = identity>
33concept mergeable =
34    input_iterator<_Input1> && input_iterator<_Input2> && weakly_incrementable<_Output> &&
35    indirectly_copyable<_Input1, _Output> && indirectly_copyable<_Input2, _Output> &&
36    indirect_strict_weak_order<_Comp, projected<_Input1, _Proj1>, projected<_Input2, _Proj2>>;
37
38#endif // _LIBCPP_STD_VER >= 20
39
40_LIBCPP_END_NAMESPACE_STD
41
42#endif // _LIBCPP___ITERATOR_MERGEABLE_H