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_MINMAX_ELEMENT_H
 10#define _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H
 11
 12#include <__algorithm/comp.h>
 13#include <__config>
 14#include <__functional/identity.h>
 15#include <__iterator/iterator_traits.h>
 16#include <__type_traits/invoke.h>
 17#include <__type_traits/is_callable.h>
 18#include <__utility/pair.h>
 19
 20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 21#  pragma GCC system_header
 22#endif
 23
 24_LIBCPP_BEGIN_NAMESPACE_STD
 25
 26template <class _Comp, class _Proj>
 27class _MinmaxElementLessFunc {
 28  _Comp& __comp_;
 29  _Proj& __proj_;
 30
 31public:
 32  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _MinmaxElementLessFunc(_Comp& __comp, _Proj& __proj)
 33      : __comp_(__comp), __proj_(__proj) {}
 34
 35  template <class _Iter>
 36  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool operator()(_Iter& __it1, _Iter& __it2) {
 37    return std::__invoke(__comp_, std::__invoke(__proj_, *__it1), std::__invoke(__proj_, *__it2));
 38  }
 39};
 40
 41template <class _Iter, class _Sent, class _Proj, class _Comp>
 42_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter, _Iter>
 43__minmax_element_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
 44  auto __less = _MinmaxElementLessFunc<_Comp, _Proj>(__comp, __proj);
 45
 46  pair<_Iter, _Iter> __result(__first, __first);
 47  if (__first == __last || ++__first == __last)
 48    return __result;
 49
 50  if (__less(__first, __result.first))
 51    __result.first = __first;
 52  else
 53    __result.second = __first;
 54
 55  while (++__first != __last) {
 56    _Iter __i = __first;
 57    if (++__first == __last) {
 58      if (__less(__i, __result.first))
 59        __result.first = __i;
 60      else if (!__less(__i, __result.second))
 61        __result.second = __i;
 62      return __result;
 63    }
 64
 65    if (__less(__first, __i)) {
 66      if (__less(__first, __result.first))
 67        __result.first = __first;
 68      if (!__less(__i, __result.second))
 69        __result.second = __i;
 70    } else {
 71      if (__less(__i, __result.first))
 72        __result.first = __i;
 73      if (!__less(__first, __result.second))
 74        __result.second = __first;
 75    }
 76  }
 77
 78  return __result;
 79}
 80
 81template <class _ForwardIterator, class _Compare>
 82[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_ForwardIterator, _ForwardIterator>
 83minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) {
 84  static_assert(
 85      __has_forward_iterator_category<_ForwardIterator>::value, "std::minmax_element requires a ForwardIterator");
 86  static_assert(
 87      __is_callable<_Compare&, decltype(*__first), decltype(*__first)>::value, "The comparator has to be callable");
 88  auto __proj = __identity();
 89  return std::__minmax_element_impl(__first, __last, __comp, __proj);
 90}
 91
 92template <class _ForwardIterator>
 93[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_ForwardIterator, _ForwardIterator>
 94minmax_element(_ForwardIterator __first, _ForwardIterator __last) {
 95  return std::minmax_element(__first, __last, __less<>());
 96}
 97
 98_LIBCPP_END_NAMESPACE_STD
 99
100#endif // _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H