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 <__utility/forward.h>
17#include <type_traits>
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 > 17
26
27struct __compose_op {
28    template<class _Fn1, class _Fn2, class ..._Args>
29    _LIBCPP_HIDE_FROM_ABI
30    constexpr auto operator()(_Fn1&& __f1, _Fn2&& __f2, _Args&&... __args) const
31        noexcept(noexcept(_VSTD::invoke(_VSTD::forward<_Fn1>(__f1), _VSTD::invoke(_VSTD::forward<_Fn2>(__f2), _VSTD::forward<_Args>(__args)...))))
32        -> decltype(      _VSTD::invoke(_VSTD::forward<_Fn1>(__f1), _VSTD::invoke(_VSTD::forward<_Fn2>(__f2), _VSTD::forward<_Args>(__args)...)))
33        { return          _VSTD::invoke(_VSTD::forward<_Fn1>(__f1), _VSTD::invoke(_VSTD::forward<_Fn2>(__f2), _VSTD::forward<_Args>(__args)...)); }
34};
35
36template <class _Fn1, class _Fn2>
37struct __compose_t : __perfect_forward<__compose_op, _Fn1, _Fn2> {
38    using __perfect_forward<__compose_op, _Fn1, _Fn2>::__perfect_forward;
39};
40
41template <class _Fn1, class _Fn2>
42_LIBCPP_HIDE_FROM_ABI
43constexpr auto __compose(_Fn1&& __f1, _Fn2&& __f2)
44    noexcept(noexcept(__compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(_VSTD::forward<_Fn1>(__f1), _VSTD::forward<_Fn2>(__f2))))
45    -> decltype(      __compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(_VSTD::forward<_Fn1>(__f1), _VSTD::forward<_Fn2>(__f2)))
46    { return          __compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(_VSTD::forward<_Fn1>(__f1), _VSTD::forward<_Fn2>(__f2)); }
47
48#endif // _LIBCPP_STD_VER > 17
49
50_LIBCPP_END_NAMESPACE_STD
51
52#endif // _LIBCPP___FUNCTIONAL_COMPOSE_H
53