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___FUNCTIONAL_BIND_FRONT_H
11#define _LIBCPP___FUNCTIONAL_BIND_FRONT_H
12
13#include <__config>
14#include <__functional/invoke.h>
15#include <__functional/perfect_forward.h>
16#include <__type_traits/conjunction.h>
17#include <__type_traits/decay.h>
18#include <__type_traits/enable_if.h>
19#include <__type_traits/is_constructible.h>
20#include <__utility/forward.h>
21
22#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23#  pragma GCC system_header
24#endif
25
26_LIBCPP_BEGIN_NAMESPACE_STD
27
28#if _LIBCPP_STD_VER >= 20
29
30struct __bind_front_op {
31  template <class... _Args>
32  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const noexcept(
33      noexcept(std::invoke(std::forward<_Args>(__args)...))) -> decltype(std::invoke(std::forward<_Args>(__args)...)) {
34    return std::invoke(std::forward<_Args>(__args)...);
35  }
36};
37
38template <class _Fn, class... _BoundArgs>
39struct __bind_front_t : __perfect_forward<__bind_front_op, _Fn, _BoundArgs...> {
40  using __perfect_forward<__bind_front_op, _Fn, _BoundArgs...>::__perfect_forward;
41};
42
43template <class _Fn, class... _Args>
44  requires is_constructible_v<decay_t<_Fn>, _Fn> && is_move_constructible_v<decay_t<_Fn>> &&
45           (is_constructible_v<decay_t<_Args>, _Args> && ...) && (is_move_constructible_v<decay_t<_Args>> && ...)
46_LIBCPP_HIDE_FROM_ABI constexpr auto bind_front(_Fn&& __f, _Args&&... __args) {
47  return __bind_front_t<decay_t<_Fn>, decay_t<_Args>...>(std::forward<_Fn>(__f), std::forward<_Args>(__args)...);
48}
49
50#endif // _LIBCPP_STD_VER >= 20
51
52_LIBCPP_END_NAMESPACE_STD
53
54#endif // _LIBCPP___FUNCTIONAL_BIND_FRONT_H