libcxx/include/__iterator/distance.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___ITERATOR_DISTANCE_H
  11 #define _LIBCPP___ITERATOR_DISTANCE_H
  12
  13 #include <__config>
  14 #include <__iterator/concepts.h>
  15 #include <__iterator/incrementable_traits.h>
  16 #include <__iterator/iterator_traits.h>
  17 #include <__ranges/access.h>
  18 #include <__ranges/concepts.h>
  19 #include <__ranges/size.h>
  20 #include <__type_traits/decay.h>
  21 #include <__type_traits/remove_cvref.h>
  22
  23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  24 #  pragma GCC system_header
  25 #endif
  26
  27 _LIBCPP_BEGIN_NAMESPACE_STD
  28
  29 template <class _InputIter>
  30 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type
  31 __distance(_InputIter __first, _InputIter __last, input_iterator_tag) {
  32   typename iterator_traits<_InputIter>::difference_type __r(0);
  33   for (; __first != __last; ++__first)
  34     ++__r;
  35   return __r;
  36 }
  37
  38 template <class _RandIter>
  39 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_RandIter>::difference_type
  40 __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag) {
  41   return __last - __first;
  42 }
  43
  44 template <class _InputIter>
  45 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type
  46 distance(_InputIter __first, _InputIter __last) {
  47   return std::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
  48 }
  49
  50 #if _LIBCPP_STD_VER >= 20
  51
  52 // [range.iter.op.distance]
  53
  54 namespace ranges {
  55 namespace __distance {
  56
  57 struct __fn {
  58   template <class _Ip, sentinel_for<_Ip> _Sp>
  59     requires(!sized_sentinel_for<_Sp, _Ip>)
  60   _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const {
  61     iter_difference_t<_Ip> __n = 0;
  62     while (__first != __last) {
  63       ++__first;
  64       ++__n;
  65     }
  66     return __n;
  67   }
  68
  69   template <class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp>
  70   _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip&& __first, _Sp __last) const {
  71     if constexpr (sized_sentinel_for<_Sp, __remove_cvref_t<_Ip>>) {
  72       return __last - __first;
  73     } else {
  74       return __last - decay_t<_Ip>(__first);
  75     }
  76   }
  77
  78   template <range _Rp>
  79   _LIBCPP_HIDE_FROM_ABI constexpr range_difference_t<_Rp> operator()(_Rp&& __r) const {
  80     if constexpr (sized_range<_Rp>) {
  81       return static_cast<range_difference_t<_Rp>>(ranges::size(__r));
  82     } else {
  83       return operator()(ranges::begin(__r), ranges::end(__r));
  84     }
  85   }
  86 };
  87
  88 } // namespace __distance
  89
  90 inline namespace __cpo {
  91 inline constexpr auto distance = __distance::__fn{};
  92 } // namespace __cpo
  93 } // namespace ranges
  94
  95 #endif // _LIBCPP_STD_VER >= 20
  96
  97 _LIBCPP_END_NAMESPACE_STD
  98
  99 #endif // _LIBCPP___ITERATOR_DISTANCE_H