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&> 54 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> 67 operator()(initializer_list<_Type> __il, _Comp __comp = {}, _Proj __proj = {}) const { 68 _LIBCPP_ASSERT_UNCATEGORIZED(__il.begin() != __il.end(), "initializer_list has to contain at least one element"); 69 auto __iters = std::__minmax_element_impl(__il.begin(), __il.end(), __comp, __proj); 70 return ranges::minmax_result<_Type>{*__iters.first, *__iters.second}; 71 } 72 73 template <input_range _Range, 74 class _Proj = identity, 75 indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less> 76 requires indirectly_copyable_storable<iterator_t<_Range>, range_value_t<_Range>*> 77 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<range_value_t<_Range>> 78 operator()(_Range&& __r, _Comp __comp = {}, _Proj __proj = {}) const { 79 auto __first = ranges::begin(__r); 80 auto __last = ranges::end(__r); 81 using _ValueT = range_value_t<_Range>; 82 83 _LIBCPP_ASSERT_UNCATEGORIZED(__first != __last, "range has to contain at least one element"); 84 85 if constexpr (forward_range<_Range>) { 86 // Special-case the one element case. Avoid repeatedly initializing objects from the result of an iterator 87 // dereference when doing so might not be idempotent. The `if constexpr` avoids the extra branch in cases where 88 // it's not needed. 89 if constexpr (!same_as<remove_cvref_t<range_reference_t<_Range>>, _ValueT> || 90 is_rvalue_reference_v<range_reference_t<_Range>>) { 91 if (ranges::next(__first) == __last) { 92 // During initialization, members are allowed to refer to already initialized members 93 // (see http://eel.is/c++draft/dcl.init.aggr#6) 94 minmax_result<_ValueT> __result = {*__first, __result.min}; 95 return __result; 96 } 97 } 98 auto __result = std::__minmax_element_impl(__first, __last, __comp, __proj); 99 return {*__result.first, *__result.second}; 100 } else { 101 // input_iterators can't be copied, so the implementation for input_iterators has to store 102 // the values instead of a pointer to the correct values 103 auto __less = [&](auto&& __a, auto&& __b) -> bool { 104 return std::invoke(__comp, 105 std::invoke(__proj, std::forward<decltype(__a)>(__a)), 106 std::invoke(__proj, std::forward<decltype(__b)>(__b))); 107 }; 108 109 // During initialization, members are allowed to refer to already initialized members 110 // (see http://eel.is/c++draft/dcl.init.aggr#6) 111 ranges::minmax_result<_ValueT> __result = {*__first, __result.min}; 112 if (__first == __last || ++__first == __last) 113 return __result; 114 115 if (__less(*__first, __result.min)) 116 __result.min = *__first; 117 else 118 __result.max = *__first; 119 120 while (++__first != __last) { 121 _ValueT __i = *__first; 122 if (++__first == __last) { 123 if (__less(__i, __result.min)) 124 __result.min = __i; 125 else if (!__less(__i, __result.max)) 126 __result.max = __i; 127 return __result; 128 } 129 130 if (__less(*__first, __i)) { 131 if (__less(*__first, __result.min)) 132 __result.min = *__first; 133 if (!__less(__i, __result.max)) 134 __result.max = std::move(__i); 135 } else { 136 if (__less(__i, __result.min)) 137 __result.min = std::move(__i); 138 if (!__less(*__first, __result.max)) 139 __result.max = *__first; 140 } 141 } 142 return __result; 143 } 144 } 145 }; 146 } // namespace __minmax 147 148 inline namespace __cpo { 149 inline constexpr auto minmax = __minmax::__fn{}; 150 } // namespace __cpo 151 } // namespace ranges 152 153 _LIBCPP_END_NAMESPACE_STD 154 155 _LIBCPP_POP_MACROS 156 157 #endif // _LIBCPP_STD_VER >= 20 158 159 #endif // _LIBCPP___ALGORITHM_RANGES_MINMAX_H 160