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_COMPOSE_H
11#define _LIBCPP___FUNCTIONAL_COMPOSE_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
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
27struct __compose_op {
28 template <class _Fn1, class _Fn2, class... _Args>
29 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Fn1&& __f1, _Fn2&& __f2, _Args&&... __args) const noexcept(noexcept(
30 std::invoke(std::forward<_Fn1>(__f1), std::invoke(std::forward<_Fn2>(__f2), std::forward<_Args>(__args)...))))
31 -> decltype(std::invoke(std::forward<_Fn1>(__f1),
32 std::invoke(std::forward<_Fn2>(__f2), std::forward<_Args>(__args)...))) {
33 return std::invoke(std::forward<_Fn1>(__f1), std::invoke(std::forward<_Fn2>(__f2), std::forward<_Args>(__args)...));
34 }
35};
36
37template <class _Fn1, class _Fn2>
38struct __compose_t : __perfect_forward<__compose_op, _Fn1, _Fn2> {
39 using __perfect_forward<__compose_op, _Fn1, _Fn2>::__perfect_forward;
40};
41
42template <class _Fn1, class _Fn2>
43_LIBCPP_HIDE_FROM_ABI constexpr auto __compose(_Fn1&& __f1, _Fn2&& __f2) noexcept(
44 noexcept(__compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(std::forward<_Fn1>(__f1), std::forward<_Fn2>(__f2))))
45 -> decltype(__compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(std::forward<_Fn1>(__f1), std::forward<_Fn2>(__f2))) {
46 return __compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(std::forward<_Fn1>(__f1), std::forward<_Fn2>(__f2));
47}
48
49#endif // _LIBCPP_STD_VER >= 20
50
51_LIBCPP_END_NAMESPACE_STD
52
53#endif // _LIBCPP___FUNCTIONAL_COMPOSE_H
54