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 27 struct __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 37 template <class _Fn1, class _Fn2> 38 struct __compose_t : __perfect_forward<__compose_op, _Fn1, _Fn2> { 39 using __perfect_forward<__compose_op, _Fn1, _Fn2>::__perfect_forward; 40 }; 41 42 template <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