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/iterator_traits.h>
  15
  16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  17 #pragma GCC system_header
  18 #endif
  19
  20 _LIBCPP_BEGIN_NAMESPACE_STD
  21
  22 template <class _InputIter>
  23 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  24 typename iterator_traits<_InputIter>::difference_type
  25 __distance(_InputIter __first, _InputIter __last, input_iterator_tag)
  26 {
  27     typename iterator_traits<_InputIter>::difference_type __r(0);
  28     for (; __first != __last; ++__first)
  29         ++__r;
  30     return __r;
  31 }
  32
  33 template <class _RandIter>
  34 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  35 typename iterator_traits<_RandIter>::difference_type
  36 __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
  37 {
  38     return __last - __first;
  39 }
  40
  41 template <class _InputIter>
  42 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  43 typename iterator_traits<_InputIter>::difference_type
  44 distance(_InputIter __first, _InputIter __last)
  45 {
  46     return _VSTD::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
  47 }
  48
  49 _LIBCPP_END_NAMESPACE_STD
  50
  51 #endif // _LIBCPP___ITERATOR_DISTANCE_H