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### 1011. `next/prev` wrong iterator type

Section: 23.4.3 [iterator.operations] Status: C++11 Submitter: Alisdair Meredith Opened: 2009-03-11 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Addresses UK 271

`next/prev` return an incremented iterator without changing the value of the original iterator. However, even this may invalidate an `InputIterator`. A `ForwardIterator` is required to guarantee the 'multipass' property.

[ Batavia (2009-05): ]

> We agree with the proposed resolution. Move to Tentatively Ready.

[ 2009-07 Frankfurt ]

> Moved from Tentatively Ready to Open only because the wording needs to be tweaked for concepts removal.

[ 2009-10-14 Daniel provided de-conceptified wording. ]

[ 2009-10 Santa Cruz: ]

> Moved to Ready.

Proposed resolution:

1. Change header `<iterator>` synopsis 23.2 [iterator.synopsis] as indicated:

   >     // 24.4.4, iterator operations:
   >     ...
   >     template <class InputForwardIterator>
   >       InputForwardIterator
   >       next(InputForwardIterator x, typename std::iterator_traits<InputForwardIterator>::difference_type n = 1);

2. Change 23.4.3 [iterator.operations] before p.6 as indicated:

   >     template <class InputForwardIterator>
   >       InputForwardIterator
   >       next(InputForwardIterator x, typename std::iterator_traits<InputForwardIterator>::difference_type n = 1);