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