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 <__utility/pair.h>
17#include <type_traits>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20#  pragma GCC system_header
21#endif
22
23_LIBCPP_BEGIN_NAMESPACE_STD
24
25template <class _Comp, class _Proj>
26class _MinmaxElementLessFunc {
27  _Comp& __comp_;
28  _Proj& __proj_;
29
30public:
31  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
32  _MinmaxElementLessFunc(_Comp& __comp, _Proj& __proj) : __comp_(__comp), __proj_(__proj) {}
33
34  template <class _Iter>
35  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
36  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
43pair<_Iter, _Iter> __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_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
83pair<_ForwardIterator, _ForwardIterator>
84minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) {
85  static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
86                "std::minmax_element requires a ForwardIterator");
87  static_assert(__is_callable<_Compare, decltype(*__first), decltype(*__first)>::value,
88                "The comparator has to be callable");
89  auto __proj = __identity();
90  return std::__minmax_element_impl(__first, __last, __comp, __proj);
91}
92
93template <class _ForwardIterator>
94_LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
95pair<_ForwardIterator, _ForwardIterator> minmax_element(_ForwardIterator __first, _ForwardIterator __last) {
96    return std::minmax_element(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
97}
98
99_LIBCPP_END_NAMESPACE_STD
100
101#endif // _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H
102