libcxx/include/__iterator/next.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_NEXT_H
  11 #define _LIBCPP___ITERATOR_NEXT_H
  12
  13 #include <__config>
  14 #include <__debug>
  15 #include <__function_like.h>
  16 #include <__iterator/advance.h>
  17 #include <__iterator/concepts.h>
  18 #include <__iterator/incrementable_traits.h>
  19 #include <__iterator/iterator_traits.h>
  20 #include <type_traits>
  21
  22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  23 #pragma GCC system_header
  24 #endif
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 template <class _InputIter>
  29 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  30     typename enable_if<__is_cpp17_input_iterator<_InputIter>::value, _InputIter>::type
  31     next(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
  32   _LIBCPP_ASSERT(__n >= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
  33                  "Attempt to next(it, n) with negative n on a non-bidirectional iterator");
  34
  35   _VSTD::advance(__x, __n);
  36   return __x;
  37 }
  38
  39 #if !defined(_LIBCPP_HAS_NO_RANGES)
  40
  41 // [range.iter.op.next]
  42
  43 namespace ranges {
  44 namespace __next {
  45
  46 struct __fn final : private __function_like {
  47   _LIBCPP_HIDE_FROM_ABI
  48   constexpr explicit __fn(__tag __x) noexcept : __function_like(__x) {}
  49
  50   template <input_or_output_iterator _Ip>
  51   _LIBCPP_HIDE_FROM_ABI
  52   constexpr _Ip operator()(_Ip __x) const {
  53     ++__x;
  54     return __x;
  55   }
  56
  57   template <input_or_output_iterator _Ip>
  58   _LIBCPP_HIDE_FROM_ABI
  59   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
  60     ranges::advance(__x, __n);
  61     return __x;
  62   }
  63
  64   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
  65   _LIBCPP_HIDE_FROM_ABI
  66   constexpr _Ip operator()(_Ip __x, _Sp __bound) const {
  67     ranges::advance(__x, __bound);
  68     return __x;
  69   }
  70
  71   template <input_or_output_iterator _Ip, sentinel_for<_Ip> _Sp>
  72   _LIBCPP_HIDE_FROM_ABI
  73   constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n, _Sp __bound) const {
  74     ranges::advance(__x, __n, __bound);
  75     return __x;
  76   }
  77 };
  78
  79 } // namespace __next
  80
  81 inline namespace __cpo {
  82   inline constexpr auto next = __next::__fn(__function_like::__tag());
  83 } // namespace __cpo
  84 } // namespace ranges
  85
  86 #endif // !defined(_LIBCPP_HAS_NO_RANGES)
  87
  88 _LIBCPP_END_NAMESPACE_STD
  89
  90 #endif // _LIBCPP___ITERATOR_NEXT_H