libcxx/include/__algorithm/ranges_max.h

   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_MAX_H
  10 #define _LIBCPP___ALGORITHM_RANGES_MAX_H
  11
  12 #include <__algorithm/ranges_min_element.h>
  13 #include <__assert>
  14 #include <__concepts/copyable.h>
  15 #include <__config>
  16 #include <__functional/identity.h>
  17 #include <__functional/invoke.h>
  18 #include <__functional/ranges_operations.h>
  19 #include <__iterator/concepts.h>
  20 #include <__iterator/projected.h>
  21 #include <__ranges/access.h>
  22 #include <__ranges/concepts.h>
  23 #include <__type_traits/is_trivially_copyable.h>
  24 #include <__utility/move.h>
  25 #include <initializer_list>
  26
  27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  28 #  pragma GCC system_header
  29 #endif
  30
  31 #if _LIBCPP_STD_VER >= 20
  32
  33 _LIBCPP_PUSH_MACROS
  34 #  include <__undef_macros>
  35
  36 _LIBCPP_BEGIN_NAMESPACE_STD
  37
  38 namespace ranges {
  39 namespace __max {
  40 struct __fn {
  41   template <class _Tp,
  42             class _Proj                                                    = identity,
  43             indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
  44   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr const _Tp&
  45   operator()(_LIBCPP_LIFETIMEBOUND const _Tp& __a,
  46              _LIBCPP_LIFETIMEBOUND const _Tp& __b,
  47              _Comp __comp = {},
  48              _Proj __proj = {}) const {
  49     return std::invoke(__comp, std::invoke(__proj, __a), std::invoke(__proj, __b)) ? __b : __a;
  50   }
  51
  52   template <copyable _Tp,
  53             class _Proj                                                    = identity,
  54             indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
  55   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Tp
  56   operator()(initializer_list<_Tp> __il, _Comp __comp = {}, _Proj __proj = {}) const {
  57     _LIBCPP_ASSERT_UNCATEGORIZED(__il.begin() != __il.end(), "initializer_list must contain at least one element");
  58
  59     auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
  60     return *ranges::__min_element_impl(__il.begin(), __il.end(), __comp_lhs_rhs_swapped, __proj);
  61   }
  62
  63   template <input_range _Rp,
  64             class _Proj                                                         = identity,
  65             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
  66     requires indirectly_copyable_storable<iterator_t<_Rp>, range_value_t<_Rp>*>
  67   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr range_value_t<_Rp>
  68   operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
  69     auto __first = ranges::begin(__r);
  70     auto __last  = ranges::end(__r);
  71
  72     _LIBCPP_ASSERT_UNCATEGORIZED(__first != __last, "range must contain at least one element");
  73
  74     if constexpr (forward_range<_Rp> && !__is_cheap_to_copy<range_value_t<_Rp>>) {
  75       auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
  76       return *ranges::__min_element_impl(std::move(__first), std::move(__last), __comp_lhs_rhs_swapped, __proj);
  77     } else {
  78       range_value_t<_Rp> __result = *__first;
  79       while (++__first != __last) {
  80         if (std::invoke(__comp, std::invoke(__proj, __result), std::invoke(__proj, *__first)))
  81           __result = *__first;
  82       }
  83       return __result;
  84     }
  85   }
  86 };
  87 } // namespace __max
  88
  89 inline namespace __cpo {
  90 inline constexpr auto max = __max::__fn{};
  91 } // namespace __cpo
  92 } // namespace ranges
  93
  94 _LIBCPP_END_NAMESPACE_STD
  95
  96 _LIBCPP_POP_MACROS
  97
  98 #endif // _LIBCPP_STD_VER >= 20 &&
  99
 100 #endif // _LIBCPP___ALGORITHM_RANGES_MAX_H