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std::ranges::chunk_by_view<V,Pred>::find_next, std::ranges::chunk_by_view<V,Pred>::find_prev - cppreference.com

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std::ranges::chunk_by_view::next

constexpr ranges::iterator_t<V> /*find-next*/( ranges::iterator_t<V> current );

 (since C++23)
(exposition only*)

Finds the next chunk.

Let base_ and pred_ be appropriate underlying data-members of chunk_by_view.

Equivalent to 

return ranges::next
(
    ranges::adjacent_find
    (
        current, ranges::end(base_), std::not_fn(std::ref(*pred_))
    ),
    1, ranges::end(base_)
);

The behavior is undefined if pred_.has_value() is false before the call to this function.

Used in the following non-static member functions:

Parameters

current - the iterator to current element in adapted view

Return value

An iterator to the next chunk, as described above.

std::ranges::chunk_by_view::prev

constexpr ranges::iterator_t<V> /*find-prev*/( ranges::iterator_t<V> current ) requires ranges::bidirectional_range<V>;

 (since C++23)
(exposition only*)

Finds the previous chunk.

Let base_ and pred_ be appropriate underlying data-members of chunk_by_view.

Returns an iterator i in the range [ranges::begin(base_), current) such that:

  • ranges::adjacent_find(i, current, std::not_fn(std::ref(*pred_))) is equal to current, and
  • if i is not equal to ranges::begin(base_), then bool(std::invoke(*pred_, *ranges::prev(i), *i)) is false.

The behavior is undefined if before the call to this function current == ranges::begin(base_) or pred_.has_value() != true.

Used in the following non-static member functions:

Parameters

current - the iterator to current element in adapted view

Return value

An iterator to the previous chunk, as described above.