libcxx/include/__algorithm/max_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_MAX_ELEMENT_H
  10 #define _LIBCPP___ALGORITHM_MAX_ELEMENT_H
  11
  12 #include <__algorithm/comp.h>
  13 #include <__algorithm/comp_ref_type.h>
  14 #include <__config>
  15 #include <__iterator/iterator_traits.h>
  16 #include <__type_traits/is_callable.h>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 template <class _Compare, class _ForwardIterator>
  25 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
  26 __max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) {
  27   static_assert(
  28       __has_forward_iterator_category<_ForwardIterator>::value, "std::max_element requires a ForwardIterator");
  29   if (__first != __last) {
  30     _ForwardIterator __i = __first;
  31     while (++__i != __last)
  32       if (__comp(*__first, *__i))
  33         __first = __i;
  34   }
  35   return __first;
  36 }
  37
  38 template <class _ForwardIterator, class _Compare>
  39 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
  40 max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp) {
  41   static_assert(
  42       __is_callable<_Compare&, decltype(*__first), decltype(*__first)>::value, "The comparator has to be callable");
  43   return std::__max_element<__comp_ref_type<_Compare> >(__first, __last, __comp);
  44 }
  45
  46 template <class _ForwardIterator>
  47 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator
  48 max_element(_ForwardIterator __first, _ForwardIterator __last) {
  49   return std::max_element(__first, __last, __less<>());
  50 }
  51
  52 _LIBCPP_END_NAMESPACE_STD
  53
  54 #endif // _LIBCPP___ALGORITHM_MAX_ELEMENT_H