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_RANGES_MINMAX_H 10 #define _LIBCPP___ALGORITHM_RANGES_MINMAX_H 11 12 #include <__algorithm/min_max_result.h> 13 #include <__algorithm/minmax_element.h> 14 #include <__assert> 15 #include <__concepts/copyable.h> 16 #include <__concepts/same_as.h> 17 #include <__config> 18 #include <__functional/identity.h> 19 #include <__functional/invoke.h> 20 #include <__functional/ranges_operations.h> 21 #include <__iterator/concepts.h> 22 #include <__iterator/next.h> 23 #include <__iterator/projected.h> 24 #include <__ranges/access.h> 25 #include <__ranges/concepts.h> 26 #include <__type_traits/is_reference.h> 27 #include <__type_traits/remove_cvref.h> 28 #include <__utility/forward.h> 29 #include <__utility/move.h> 30 #include <__utility/pair.h> 31 #include <initializer_list> 32 33 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 34 # pragma GCC system_header 35 #endif 36 37 #if _LIBCPP_STD_VER >= 20 38 39 _LIBCPP_PUSH_MACROS 40 # include <__undef_macros> 41 42 _LIBCPP_BEGIN_NAMESPACE_STD 43 44 namespace ranges { 45 template <class _T1> 46 using minmax_result = min_max_result<_T1>; 47 48 namespace __minmax { 49 struct __fn { 50 template <class _Type, 51 class _Proj = identity, 52 indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less> 53 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<const _Type&> operator__fn54 operator()(_LIBCPP_LIFETIMEBOUND const _Type& __a, 55 _LIBCPP_LIFETIMEBOUND const _Type& __b, 56 _Comp __comp = {}, 57 _Proj __proj = {}) const { 58 if (std::invoke(__comp, std::invoke(__proj, __b), std::invoke(__proj, __a))) 59 return {__b, __a}; 60 return {__a, __b}; 61 } 62 63 template <copyable _Type, 64 class _Proj = identity, 65 indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less> 66 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<_Type> operator__fn67 operator()(initializer_list<_Type> __il, _Comp __comp = {}, _Proj __proj = {}) const { 68 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 69 __il.begin() != __il.end(), "initializer_list has to contain at least one element"); 70 auto __iters = std::__minmax_element_impl(__il.begin(), __il.end(), __comp, __proj); 71 return ranges::minmax_result<_Type>{*__iters.first, *__iters.second}; 72 } 73 74 template <input_range _Range, 75 class _Proj = identity, 76 indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less> 77 requires indirectly_copyable_storable<iterator_t<_Range>, range_value_t<_Range>*> 78 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<range_value_t<_Range>> operator__fn79 operator()(_Range&& __r, _Comp __comp = {}, _Proj __proj = {}) const { 80 auto __first = ranges::begin(__r); 81 auto __last = ranges::end(__r); 82 using _ValueT = range_value_t<_Range>; 83 84 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__first != __last, "range has to contain at least one element"); 85 86 if constexpr (forward_range<_Range>) { 87 // Special-case the one element case. Avoid repeatedly initializing objects from the result of an iterator 88 // dereference when doing so might not be idempotent. The `if constexpr` avoids the extra branch in cases where 89 // it's not needed. 90 if constexpr (!same_as<remove_cvref_t<range_reference_t<_Range>>, _ValueT> || 91 is_rvalue_reference_v<range_reference_t<_Range>>) { 92 if (ranges::next(__first) == __last) { 93 // During initialization, members are allowed to refer to already initialized members 94 // (see http://eel.is/c++draft/dcl.init.aggr#6) 95 minmax_result<_ValueT> __result = {*__first, __result.min}; 96 return __result; 97 } 98 } 99 auto __result = std::__minmax_element_impl(__first, __last, __comp, __proj); 100 return {*__result.first, *__result.second}; 101 } else { 102 // input_iterators can't be copied, so the implementation for input_iterators has to store 103 // the values instead of a pointer to the correct values 104 auto __less = [&](auto&& __a, auto&& __b) -> bool { 105 return std::invoke(__comp, 106 std::invoke(__proj, std::forward<decltype(__a)>(__a)), 107 std::invoke(__proj, std::forward<decltype(__b)>(__b))); 108 }; 109 110 // During initialization, members are allowed to refer to already initialized members 111 // (see http://eel.is/c++draft/dcl.init.aggr#6) 112 ranges::minmax_result<_ValueT> __result = {*__first, __result.min}; 113 if (__first == __last || ++__first == __last) 114 return __result; 115 116 if (__less(*__first, __result.min)) 117 __result.min = *__first; 118 else 119 __result.max = *__first; 120 121 while (++__first != __last) { 122 _ValueT __i = *__first; 123 if (++__first == __last) { 124 if (__less(__i, __result.min)) 125 __result.min = __i; 126 else if (!__less(__i, __result.max)) 127 __result.max = __i; 128 return __result; 129 } 130 131 if (__less(*__first, __i)) { 132 if (__less(*__first, __result.min)) 133 __result.min = *__first; 134 if (!__less(__i, __result.max)) 135 __result.max = std::move(__i); 136 } else { 137 if (__less(__i, __result.min)) 138 __result.min = std::move(__i); 139 if (!__less(*__first, __result.max)) 140 __result.max = *__first; 141 } 142 } 143 return __result; 144 } 145 } 146 }; 147 } // namespace __minmax 148 149 inline namespace __cpo { 150 inline constexpr auto minmax = __minmax::__fn{}; 151 } // namespace __cpo 152 } // namespace ranges 153 154 _LIBCPP_END_NAMESPACE_STD 155 156 _LIBCPP_POP_MACROS 157 158 #endif // _LIBCPP_STD_VER >= 20 159 160 #endif // _LIBCPP___ALGORITHM_RANGES_MINMAX_H 161