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 <__utility/forward.h>
17#include <__utility/integer_sequence.h>
18#include <tuple>
19#include <type_traits>
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 > 17
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(_VSTD::invoke(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)..., _VSTD::get<_Ip>(_VSTD::forward<_BoundArgs>(__bound_args))...)))
37        -> decltype(      _VSTD::invoke(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)..., _VSTD::get<_Ip>(_VSTD::forward<_BoundArgs>(__bound_args))...))
38        { return          _VSTD::invoke(_VSTD::forward<_Fn>(__f), _VSTD::forward<_Args>(__args)..., _VSTD::get<_Ip>(_VSTD::forward<_BoundArgs>(__bound_args))...); }
39};
40
41template <class _Fn, class _BoundArgs>
42struct __bind_back_t : __perfect_forward<__bind_back_op<tuple_size_v<_BoundArgs>>, _Fn, _BoundArgs> {
43    using __perfect_forward<__bind_back_op<tuple_size_v<_BoundArgs>>, _Fn, _BoundArgs>::__perfect_forward;
44};
45
46template <class _Fn, class ..._Args, class = enable_if_t<
47    _And<
48        is_constructible<decay_t<_Fn>, _Fn>,
49        is_move_constructible<decay_t<_Fn>>,
50        is_constructible<decay_t<_Args>, _Args>...,
51        is_move_constructible<decay_t<_Args>>...
52    >::value
53>>
54_LIBCPP_HIDE_FROM_ABI
55constexpr auto __bind_back(_Fn&& __f, _Args&&... __args)
56    noexcept(noexcept(__bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(_VSTD::forward<_Fn>(__f), _VSTD::forward_as_tuple(_VSTD::forward<_Args>(__args)...))))
57    -> decltype(      __bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(_VSTD::forward<_Fn>(__f), _VSTD::forward_as_tuple(_VSTD::forward<_Args>(__args)...)))
58    { return          __bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(_VSTD::forward<_Fn>(__f), _VSTD::forward_as_tuple(_VSTD::forward<_Args>(__args)...)); }
59
60#endif // _LIBCPP_STD_VER > 17
61
62_LIBCPP_END_NAMESPACE_STD
63
64#endif // _LIBCPP___FUNCTIONAL_BIND_BACK_H
65