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 18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19 # pragma GCC system_header 20 #endif 21 22 _LIBCPP_BEGIN_NAMESPACE_STD 23 24 #if _LIBCPP_STD_VER >= 20 25 26 struct __compose_op { 27 template<class _Fn1, class _Fn2, class ..._Args> 28 _LIBCPP_HIDE_FROM_ABI 29 constexpr auto operator()(_Fn1&& __f1, _Fn2&& __f2, _Args&&... __args) const 30 noexcept(noexcept(_VSTD::invoke(_VSTD::forward<_Fn1>(__f1), _VSTD::invoke(_VSTD::forward<_Fn2>(__f2), _VSTD::forward<_Args>(__args)...)))) 31 -> decltype( _VSTD::invoke(_VSTD::forward<_Fn1>(__f1), _VSTD::invoke(_VSTD::forward<_Fn2>(__f2), _VSTD::forward<_Args>(__args)...))) 32 { return _VSTD::invoke(_VSTD::forward<_Fn1>(__f1), _VSTD::invoke(_VSTD::forward<_Fn2>(__f2), _VSTD::forward<_Args>(__args)...)); } 33 }; 34 35 template <class _Fn1, class _Fn2> 36 struct __compose_t : __perfect_forward<__compose_op, _Fn1, _Fn2> { 37 using __perfect_forward<__compose_op, _Fn1, _Fn2>::__perfect_forward; 38 }; 39 40 template <class _Fn1, class _Fn2> 41 _LIBCPP_HIDE_FROM_ABI 42 constexpr auto __compose(_Fn1&& __f1, _Fn2&& __f2) 43 noexcept(noexcept(__compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(_VSTD::forward<_Fn1>(__f1), _VSTD::forward<_Fn2>(__f2)))) 44 -> decltype( __compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(_VSTD::forward<_Fn1>(__f1), _VSTD::forward<_Fn2>(__f2))) 45 { return __compose_t<decay_t<_Fn1>, decay_t<_Fn2>>(_VSTD::forward<_Fn1>(__f1), _VSTD::forward<_Fn2>(__f2)); } 46 47 #endif // _LIBCPP_STD_VER >= 20 48 49 _LIBCPP_END_NAMESPACE_STD 50 51 #endif // _LIBCPP___FUNCTIONAL_COMPOSE_H 52