libcxx/include/__algorithm/minmax_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_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 <__functional/invoke.h>
  16 #include <__iterator/iterator_traits.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
  26 template <class _Comp, class _Proj>
  27 class _MinmaxElementLessFunc {
  28   _Comp& __comp_;
  29   _Proj& __proj_;
  30
  31 public:
  32   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
  33   _MinmaxElementLessFunc(_Comp& __comp, _Proj& __proj) : __comp_(__comp), __proj_(__proj) {}
  34
  35   template <class _Iter>
  36   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
  37   bool operator()(_Iter& __it1, _Iter& __it2) {
  38     return std::__invoke(__comp_, std::__invoke(__proj_, *__it1), std::__invoke(__proj_, *__it2));
  39   }
  40 };
  41
  42 template <class _Iter, class _Sent, class _Proj, class _Comp>
  43 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
  44 pair<_Iter, _Iter> __minmax_element_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
  45   auto __less = _MinmaxElementLessFunc<_Comp, _Proj>(__comp, __proj);
  46
  47   pair<_Iter, _Iter> __result(__first, __first);
  48   if (__first == __last || ++__first == __last)
  49     return __result;
  50
  51   if (__less(__first, __result.first))
  52     __result.first = __first;
  53   else
  54     __result.second = __first;
  55
  56   while (++__first != __last) {
  57     _Iter __i = __first;
  58     if (++__first == __last) {
  59       if (__less(__i, __result.first))
  60         __result.first = __i;
  61       else if (!__less(__i, __result.second))
  62         __result.second = __i;
  63       return __result;
  64     }
  65
  66     if (__less(__first, __i)) {
  67       if (__less(__first, __result.first))
  68         __result.first = __first;
  69     if (!__less(__i, __result.second))
  70       __result.second = __i;
  71     } else {
  72       if (__less(__i, __result.first))
  73         __result.first = __i;
  74       if (!__less(__first, __result.second))
  75         __result.second = __first;
  76     }
  77   }
  78
  79   return __result;
  80 }
  81
  82 template <class _ForwardIterator, class _Compare>
  83 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
  84 pair<_ForwardIterator, _ForwardIterator>
  85 minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) {
  86   static_assert(__has_forward_iterator_category<_ForwardIterator>::value,
  87                 "std::minmax_element requires a ForwardIterator");
  88   static_assert(__is_callable<_Compare, decltype(*__first), decltype(*__first)>::value,
  89                 "The comparator has to be callable");
  90   auto __proj = __identity();
  91   return std::__minmax_element_impl(__first, __last, __comp, __proj);
  92 }
  93
  94 template <class _ForwardIterator>
  95 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
  96 pair<_ForwardIterator, _ForwardIterator> minmax_element(_ForwardIterator __first, _ForwardIterator __last) {
  97     return std::minmax_element(__first, __last, __less<>());
  98 }
  99
 100 _LIBCPP_END_NAMESPACE_STD
 101
 102 #endif // _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H