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_BACK_H
11#define _LIBCPP___FUNCTIONAL_BIND_BACK_H
12
13#include <__config>
14#include <__functional/invoke.h>
15#include <__functional/perfect_forward.h>
16#include <__type_traits/decay.h>
17#include <__utility/forward.h>
18#include <__utility/integer_sequence.h>
19#include <tuple>
20
21#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22# pragma GCC system_header
23#endif
24
25_LIBCPP_BEGIN_NAMESPACE_STD
26
27#if _LIBCPP_STD_VER >= 20
28
29template <size_t _NBound, class = make_index_sequence<_NBound>>
30struct __bind_back_op;
31
32template <size_t _NBound, size_t... _Ip>
33struct __bind_back_op<_NBound, index_sequence<_Ip...>> {
34 template <class _Fn, class _BoundArgs, class... _Args>
35 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Fn&& __f, _BoundArgs&& __bound_args, _Args&&... __args) const
36 noexcept(noexcept(std::invoke(std::forward<_Fn>(__f),
37 std::forward<_Args>(__args)...,
38 std::get<_Ip>(std::forward<_BoundArgs>(__bound_args))...)))
39 -> decltype(std::invoke(std::forward<_Fn>(__f),
40 std::forward<_Args>(__args)...,
41 std::get<_Ip>(std::forward<_BoundArgs>(__bound_args))...)) {
42 return std::invoke(std::forward<_Fn>(__f),
43 std::forward<_Args>(__args)...,
44 std::get<_Ip>(std::forward<_BoundArgs>(__bound_args))...);
45 }
46};
47
48template <class _Fn, class _BoundArgs>
49struct __bind_back_t : __perfect_forward<__bind_back_op<tuple_size_v<_BoundArgs>>, _Fn, _BoundArgs> {
50 using __perfect_forward<__bind_back_op<tuple_size_v<_BoundArgs>>, _Fn, _BoundArgs>::__perfect_forward;
51};
52
53template <class _Fn, class... _Args>
54 requires is_constructible_v<decay_t<_Fn>, _Fn> && is_move_constructible_v<decay_t<_Fn>> &&
55 (is_constructible_v<decay_t<_Args>, _Args> && ...) && (is_move_constructible_v<decay_t<_Args>> && ...)
56_LIBCPP_HIDE_FROM_ABI constexpr auto __bind_back(_Fn&& __f, _Args&&... __args) noexcept(
57 noexcept(__bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
58 std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...))))
59 -> decltype(__bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
60 std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...))) {
61 return __bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
62 std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...));
63}
64
65# if _LIBCPP_STD_VER >= 23
66template <class _Fn, class... _Args>
67_LIBCPP_HIDE_FROM_ABI constexpr auto bind_back(_Fn&& __f, _Args&&... __args) {
68 static_assert(is_constructible_v<decay_t<_Fn>, _Fn>, "bind_back requires decay_t<F> to be constructible from F");
69 static_assert(is_move_constructible_v<decay_t<_Fn>>, "bind_back requires decay_t<F> to be move constructible");
70 static_assert((is_constructible_v<decay_t<_Args>, _Args> && ...),
71 "bind_back requires all decay_t<Args> to be constructible from respective Args");
72 static_assert((is_move_constructible_v<decay_t<_Args>> && ...),
73 "bind_back requires all decay_t<Args> to be move constructible");
74 return __bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
75 std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...));
76}
77# endif // _LIBCPP_STD_VER >= 23
78
79#endif // _LIBCPP_STD_VER >= 20
80
81_LIBCPP_END_NAMESPACE_STD
82
83#endif // _LIBCPP___FUNCTIONAL_BIND_BACK_H
84