v1/__functional/bind_back.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___FUNCTIONAL_BIND_BACK_H
0011 #define _LIBCPP___FUNCTIONAL_BIND_BACK_H
0012
0013 #include <__config>
0014 #include <__functional/invoke.h>
0015 #include <__functional/perfect_forward.h>
0016 #include <__type_traits/decay.h>
0017 #include <__utility/forward.h>
0018 #include <__utility/integer_sequence.h>
0019 #include <tuple>
0020
0021 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0022 #  pragma GCC system_header
0023 #endif
0024
0025 _LIBCPP_BEGIN_NAMESPACE_STD
0026
0027 #if _LIBCPP_STD_VER >= 20
0028
0029 template <size_t _NBound, class = make_index_sequence<_NBound>>
0030 struct __bind_back_op;
0031
0032 template <size_t _NBound, size_t... _Ip>
0033 struct __bind_back_op<_NBound, index_sequence<_Ip...>> {
0034   template <class _Fn, class _BoundArgs, class... _Args>
0035   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Fn&& __f, _BoundArgs&& __bound_args, _Args&&... __args) const
0036       noexcept(noexcept(std::invoke(std::forward<_Fn>(__f),
0037                                     std::forward<_Args>(__args)...,
0038                                     std::get<_Ip>(std::forward<_BoundArgs>(__bound_args))...)))
0039           -> decltype(std::invoke(std::forward<_Fn>(__f),
0040                                   std::forward<_Args>(__args)...,
0041                                   std::get<_Ip>(std::forward<_BoundArgs>(__bound_args))...)) {
0042     return std::invoke(std::forward<_Fn>(__f),
0043                        std::forward<_Args>(__args)...,
0044                        std::get<_Ip>(std::forward<_BoundArgs>(__bound_args))...);
0045   }
0046 };
0047
0048 template <class _Fn, class _BoundArgs>
0049 struct __bind_back_t : __perfect_forward<__bind_back_op<tuple_size_v<_BoundArgs>>, _Fn, _BoundArgs> {
0050   using __perfect_forward<__bind_back_op<tuple_size_v<_BoundArgs>>, _Fn, _BoundArgs>::__perfect_forward;
0051 };
0052
0053 template <class _Fn, class... _Args>
0054   requires is_constructible_v<decay_t<_Fn>, _Fn> && is_move_constructible_v<decay_t<_Fn>> &&
0055                (is_constructible_v<decay_t<_Args>, _Args> && ...) && (is_move_constructible_v<decay_t<_Args>> && ...)
0056 _LIBCPP_HIDE_FROM_ABI constexpr auto __bind_back(_Fn&& __f, _Args&&... __args) noexcept(
0057     noexcept(__bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
0058         std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...))))
0059     -> decltype(__bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
0060         std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...))) {
0061   return __bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
0062       std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...));
0063 }
0064
0065 #  if _LIBCPP_STD_VER >= 23
0066 template <class _Fn, class... _Args>
0067 _LIBCPP_HIDE_FROM_ABI constexpr auto bind_back(_Fn&& __f, _Args&&... __args) {
0068   static_assert(is_constructible_v<decay_t<_Fn>, _Fn>, "bind_back requires decay_t<F> to be constructible from F");
0069   static_assert(is_move_constructible_v<decay_t<_Fn>>, "bind_back requires decay_t<F> to be move constructible");
0070   static_assert((is_constructible_v<decay_t<_Args>, _Args> && ...),
0071                 "bind_back requires all decay_t<Args> to be constructible from respective Args");
0072   static_assert((is_move_constructible_v<decay_t<_Args>> && ...),
0073                 "bind_back requires all decay_t<Args> to be move constructible");
0074   return __bind_back_t<decay_t<_Fn>, tuple<decay_t<_Args>...>>(
0075       std::forward<_Fn>(__f), std::forward_as_tuple(std::forward<_Args>(__args)...));
0076 }
0077 #  endif // _LIBCPP_STD_VER >= 23
0078
0079 #endif // _LIBCPP_STD_VER >= 20
0080
0081 _LIBCPP_END_NAMESPACE_STD
0082
0083 #endif // _LIBCPP___FUNCTIONAL_BIND_BACK_H