libcxx/include/__algorithm/ranges_min_element.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_MIN_ELEMENT_H
  10 #define _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H
  11
  12 #include <__config>
  13 #include <__functional/identity.h>
  14 #include <__functional/invoke.h>
  15 #include <__functional/ranges_operations.h>
  16 #include <__iterator/concepts.h>
  17 #include <__iterator/projected.h>
  18 #include <__ranges/access.h>
  19 #include <__ranges/concepts.h>
  20 #include <__ranges/dangling.h>
  21 #include <__utility/forward.h>
  22
  23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  24 #  pragma GCC system_header
  25 #endif
  26
  27 _LIBCPP_PUSH_MACROS
  28 #include <__undef_macros>
  29
  30 #if _LIBCPP_STD_VER >= 20
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 namespace ranges {
  35
  36 // TODO(ranges): `ranges::min_element` can now simply delegate to `std::__min_element`.
  37 template <class _Ip, class _Sp, class _Proj, class _Comp>
  38 _LIBCPP_HIDE_FROM_ABI constexpr _Ip __min_element_impl(_Ip __first, _Sp __last, _Comp& __comp, _Proj& __proj) {
  39   if (__first == __last)
  40     return __first;
  41
  42   _Ip __i = __first;
  43   while (++__i != __last)
  44     if (std::invoke(__comp, std::invoke(__proj, *__i), std::invoke(__proj, *__first)))
  45       __first = __i;
  46   return __first;
  47 }
  48
  49 struct __min_element {
  50   template <forward_iterator _Ip,
  51             sentinel_for<_Ip> _Sp,
  52             class _Proj                                             = identity,
  53             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
  54   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Ip
  55   operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
  56     return ranges::__min_element_impl(__first, __last, __comp, __proj);
  57   }
  58
  59   template <forward_range _Rp,
  60             class _Proj                                                         = identity,
  61             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
  62   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Rp>
  63   operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
  64     return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
  65   }
  66 };
  67
  68 inline namespace __cpo {
  69 inline constexpr auto min_element = __min_element{};
  70 } // namespace __cpo
  71 } // namespace ranges
  72
  73 _LIBCPP_END_NAMESPACE_STD
  74
  75 #endif // _LIBCPP_STD_VER >= 20
  76
  77 _LIBCPP_POP_MACROS
  78
  79 #endif // _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H