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 27 struct __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 36 template <class _Fn1, class _Fn2> 37 struct __compose_t : __perfect_forward<__compose_op, _Fn1, _Fn2> { 38 using __perfect_forward<__compose_op, _Fn1, _Fn2>::__perfect_forward; 39 }; 40 41 template <class _Fn1, class _Fn2> 42 _LIBCPP_HIDE_FROM_ABI 43 constexpr 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