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3397. ranges::basic_istream_view::iterator should not provide iterator_category

Section: 25.6.6.3 [range.istream.iterator] Status: C++20 Submitter: Tomasz Kamiński Opened: 2020-02-13 Last modified: 2021-02-25

Priority: 1

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Discussion:

The ranges::basic_istream_view::iterator is a move-only type, and as such it does not meets the Cpp17 iterator requirements, yet it does provides iterator_category (intended to be used for Cpp17 iterators). We should provide iterator_concept instead.

[2020-02 Status to Immediate on Thursday night in Prague.]

Proposed resolution:

This wording is relative to N4849.

1. Modify 25.6.6.3 [range.istream.iterator] as indicated:

   namespace std::ranges {
     template<class Val, class CharT, class Traits>
     class basic_istream_view<Val, CharT, Traits>::iterator { // exposition only
     public:
       using iterator_categoryiterator_concept = input_iterator_tag;
       using difference_type = ptrdiff_t;
       using value_type = Val;
   
       iterator() = default;
       […]
     };
   }