xref: /freebsd-src/contrib/llvm-project/libcxx/include/__functional/compose.h (revision cb14a3fe5122c879eae1fb480ed7ce82a699ddb6)
1349cc55cSDimitry Andric // -*- C++ -*-
2349cc55cSDimitry Andric //===----------------------------------------------------------------------===//
3349cc55cSDimitry Andric //
4349cc55cSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5349cc55cSDimitry Andric // See https://llvm.org/LICENSE.txt for license information.
6349cc55cSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7349cc55cSDimitry Andric //
8349cc55cSDimitry Andric //===----------------------------------------------------------------------===//
9349cc55cSDimitry Andric 
10349cc55cSDimitry Andric #ifndef _LIBCPP___FUNCTIONAL_COMPOSE_H
11349cc55cSDimitry Andric #define _LIBCPP___FUNCTIONAL_COMPOSE_H
12349cc55cSDimitry Andric 
13349cc55cSDimitry Andric #include <__config>
14349cc55cSDimitry Andric #include <__functional/invoke.h>
15349cc55cSDimitry Andric #include <__functional/perfect_forward.h>
1606c3fb27SDimitry Andric #include <__type_traits/decay.h>
17349cc55cSDimitry Andric #include <__utility/forward.h>
18349cc55cSDimitry Andric 
19349cc55cSDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20349cc55cSDimitry Andric #  pragma GCC system_header
21349cc55cSDimitry Andric #endif
22349cc55cSDimitry Andric 
23349cc55cSDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD
24349cc55cSDimitry Andric 
2506c3fb27SDimitry Andric #if _LIBCPP_STD_VER >= 20
26349cc55cSDimitry Andric 
27349cc55cSDimitry Andric struct __compose_op {
28349cc55cSDimitry Andric   template <class _Fn1, class _Fn2, class... _Args>
29*cb14a3feSDimitry Andric   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Fn1&& __f1, _Fn2&& __f2, _Args&&... __args) const noexcept(noexcept(
30*cb14a3feSDimitry Andric       std::invoke(std::forward<_Fn1>(__f1), std::invoke(std::forward<_Fn2>(__f2), std::forward<_Args>(__args)...))))
31*cb14a3feSDimitry Andric       -> decltype(std::invoke(std::forward<_Fn1>(__f1),
32*cb14a3feSDimitry Andric                               std::invoke(std::forward<_Fn2>(__f2), std::forward<_Args>(__args)...))) {
33*cb14a3feSDimitry Andric     return std::invoke(std::forward<_Fn1>(__f1), std::invoke(std::forward<_Fn2>(__f2), std::forward<_Args>(__args)...));
34*cb14a3feSDimitry Andric   }
35349cc55cSDimitry Andric };
36349cc55cSDimitry Andric 
37349cc55cSDimitry Andric template <class _Fn1, class _Fn2>
38349cc55cSDimitry Andric struct __compose_t : __perfect_forward<__compose_op, _Fn1, _Fn2> {
39349cc55cSDimitry Andric   using __perfect_forward<__compose_op, _Fn1, _Fn2>::__perfect_forward;
40349cc55cSDimitry Andric };
41349cc55cSDimitry Andric 
42349cc55cSDimitry Andric template <class _Fn1, class _Fn2>
43*cb14a3feSDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr auto __compose(_Fn1&& __f1, _Fn2&& __f2) noexcept(
44*cb14a3feSDimitry Andric     noexcept(__compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(std::forward<_Fn1>(__f1), std::forward<_Fn2>(__f2))))
45*cb14a3feSDimitry Andric     -> decltype(__compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(std::forward<_Fn1>(__f1), std::forward<_Fn2>(__f2))) {
46*cb14a3feSDimitry Andric   return __compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(std::forward<_Fn1>(__f1), std::forward<_Fn2>(__f2));
47*cb14a3feSDimitry Andric }
48349cc55cSDimitry Andric 
4906c3fb27SDimitry Andric #endif // _LIBCPP_STD_VER >= 20
50349cc55cSDimitry Andric 
51349cc55cSDimitry Andric _LIBCPP_END_NAMESPACE_STD
52349cc55cSDimitry Andric 
53349cc55cSDimitry Andric #endif // _LIBCPP___FUNCTIONAL_COMPOSE_H
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