1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 10 #define _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 11 12 #include <__concepts/same_as.h> 13 #include <__config> 14 #include <__functional/identity.h> 15 #include <__functional/invoke.h> 16 #include <__type_traits/decay.h> 17 #include <__type_traits/enable_if.h> 18 #include <__type_traits/integral_constant.h> 19 #include <__type_traits/invoke.h> 20 #include <__type_traits/is_member_pointer.h> 21 #include <__type_traits/is_same.h> 22 #include <__utility/declval.h> 23 #include <__utility/forward.h> 24 25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 26 # pragma GCC system_header 27 #endif 28 29 _LIBCPP_BEGIN_NAMESPACE_STD 30 31 template <class _Pred, class _Proj> 32 struct _ProjectedPred { 33 _Pred& __pred; // Can be a unary or a binary predicate. 34 _Proj& __proj; 35 36 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI _ProjectedPred(_Pred& __pred_arg, _Proj& __proj_arg) 37 : __pred(__pred_arg), __proj(__proj_arg) {} 38 39 template <class _Tp> 40 typename __invoke_of<_Pred&, decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_Tp>()))>::type 41 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI 42 operator()(_Tp&& __v) const { 43 return std::__invoke(__pred, std::__invoke(__proj, std::forward<_Tp>(__v))); 44 } 45 46 template <class _T1, class _T2> 47 typename __invoke_of<_Pred&, 48 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T1>())), 49 decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T2>()))>::type _LIBCPP_CONSTEXPR 50 _LIBCPP_HIDE_FROM_ABI 51 operator()(_T1&& __lhs, _T2&& __rhs) const { 52 return std::__invoke( 53 __pred, std::__invoke(__proj, std::forward<_T1>(__lhs)), std::__invoke(__proj, std::forward<_T2>(__rhs))); 54 } 55 }; 56 57 template < 58 class _Pred, 59 class _Proj, 60 __enable_if_t<!(!is_member_pointer<__decay_t<_Pred> >::value && __is_identity<__decay_t<_Proj> >::value), int> = 0> 61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ProjectedPred<_Pred, _Proj> __make_projected(_Pred& __pred, _Proj& __proj) { 62 return _ProjectedPred<_Pred, _Proj>(__pred, __proj); 63 } 64 65 // Avoid creating the functor and just use the pristine comparator -- for certain algorithms, this would enable 66 // optimizations that rely on the type of the comparator. Additionally, this results in less layers of indirection in 67 // the call stack when the comparator is invoked, even in an unoptimized build. 68 template < 69 class _Pred, 70 class _Proj, 71 __enable_if_t<!is_member_pointer<__decay_t<_Pred> >::value && __is_identity<__decay_t<_Proj> >::value, int> = 0> 72 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Pred& __make_projected(_Pred& __pred, _Proj&) { 73 return __pred; 74 } 75 76 _LIBCPP_END_NAMESPACE_STD 77 78 #if _LIBCPP_STD_VER >= 20 79 80 _LIBCPP_BEGIN_NAMESPACE_STD 81 82 namespace ranges { 83 84 template <class _Comp, class _Proj1, class _Proj2> 85 _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) __make_projected_comp(_Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) { 86 if constexpr (__is_identity<decay_t<_Proj1>>::value && __is_identity<decay_t<_Proj2>>::value && 87 !is_member_pointer_v<decay_t<_Comp>>) { 88 // Avoid creating the lambda and just use the pristine comparator -- for certain algorithms, this would enable 89 // optimizations that rely on the type of the comparator. 90 return __comp; 91 92 } else { 93 return [&](auto&& __lhs, auto&& __rhs) -> bool { 94 return std::invoke(__comp, 95 std::invoke(__proj1, std::forward<decltype(__lhs)>(__lhs)), 96 std::invoke(__proj2, std::forward<decltype(__rhs)>(__rhs))); 97 }; 98 } 99 } 100 101 } // namespace ranges 102 103 _LIBCPP_END_NAMESPACE_STD 104 105 #endif // _LIBCPP_STD_VER >= 20 106 107 #endif // _LIBCPP___ALGORITHM_MAKE_PROJECTED_H 108