std::ranges:: views:: chunk, std::ranges:: chunk_view

chunk_view takes a view and a number n and produces a range of views (the chunks ) of the original view, such that each chunk , except maybe the last one, has the size n . These chunks are non-overlapping, successive sub-ranges of the elements of the original view, in order.

Let s be the size of the original view. If s is not the multiple of n , the size of the last produced view is exactly s % n (the remainder). Otherwise, the size of each chunk , including the last one, is n .

The size of produced view is /*div-ceil*/ ( s ) .

If the n is not greater than ​ 0 ​ the behavior is undefined.

I r = num / denom;
if (num % denom)
    ++r;
return r;

Data members

Member functions

Deduction guides

Nested classes

Helper templates

This specialization of ranges::enable_borrowed_range makes chunk_view satisfy borrowed_range when the underlying view V satisfies both, the forward_range and the borrowed_range .

Notes

If V models input_range ( 1 ) , chunk_view 's iterator has a dedicated type: outer_iterator::value_type that is itself an input view.

If V models forward_range or stronger ( 2 ) , chunk_view defers to views::take for its value_type .

If V models bidirectional_range or stronger ranges ( 2 ) , the need to calculate size the last chunk correctly (from the end iterator ) requires the underlying range type V to be sized_range .

Example

#include <algorithm>
#include <iostream>
#include <ranges>
 
auto print_subrange = [](std::ranges::viewable_range auto&& r)
{
    std::cout << '[';
    for (int pos{}; auto elem : r)
        std::cout << (pos++ ? " " : "") << elem;
    std::cout << "] ";
};
 
int main()
{
    const auto v = {1, 2, 3, 4, 5, 6};
 
    for (const unsigned width : std::views::iota(1U, 2U + v.size()))
    {
        auto const chunks = v | std::views::chunk(width);
        std::cout << "chunk(" << width << "): ";
        std::ranges::for_each(chunks, print_subrange);
        std::cout << '\n';
    }
}

chunk(1): [1] [2] [3] [4] [5] [6]
chunk(2): [1 2] [3 4] [5 6]
chunk(3): [1 2 3] [4 5 6]
chunk(4): [1 2 3 4] [5 6]
chunk(5): [1 2 3 4 5] [6]
chunk(6): [1 2 3 4 5 6]
chunk(7): [1 2 3 4 5 6]

References

See also