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3707. chunk_view::outer-iterator::value_type::size should return unsigned type

Section: [range.chunk.outer.value] Status: C++23 Submitter: Hewill Kang Opened: 2022-06-01 Last modified: 2023-11-22

Priority: Not Prioritized

View all other issues in [range.chunk.outer.value].

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Currently, the size function of chunk_view::outer-iterator::value_type returns the result of ranges::min, since the operands are of type range_difference_t<V>, this will return a signed type, which is inconsistent with the return type of size of the forward-version of chunk_view::iterator::value_type ( [range.chunk.fwd.iter]), which always returns an unsigned type.

I think it's more reasonable to return an unsigned type, since this is intentional behavior and doesn't fall back to using the default view_interface::size. And if LWG 3646 is eventually adopted, there's no reason why it shouldn't be made unsigned.

[2022-06-21; Reflector poll]

Set status to Tentatively Ready after five votes in favour during reflector poll.

[2022-07-15; LWG telecon: move to Ready]

[2022-07-25 Approved at July 2022 virtual plenary. Status changed: Ready → WP.]

Proposed resolution:

This wording is relative to N4910.

  1. Modify [range.chunk.outer.value] as indicated:

    constexpr auto size() const
      requires sized_sentinel_for<sentinel_t<V>, iterator_t<V>>;

    -4- Effects: Equivalent to:

    return to-unsigned-like(ranges::min(parent_->remainder_, ranges::end(parent_->base_) - *parent_->current_));