libcxx/include/__cxx03/__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 <__cxx03/__algorithm/comp.h>
  13 #include <__cxx03/__config>
  14 #include <__cxx03/__functional/identity.h>
  15 #include <__cxx03/__functional/invoke.h>
  16 #include <__cxx03/__iterator/iterator_traits.h>
  17 #include <__cxx03/__type_traits/is_callable.h>
  18 #include <__cxx03/__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 _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
  41 template <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
  81 template <class _ForwardIterator, class _Compare>
  82 _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_ForwardIterator, _ForwardIterator>
  83 minmax_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
  92 template <class _ForwardIterator>
  93 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_ForwardIterator, _ForwardIterator>
  94 minmax_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