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

 

C++

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Feature test macros (C++20)

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Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

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Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range conversions
to (C++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)	elements_of (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Range factories
empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (C++23)(C++23)	basic_istream_viewviews::istream
Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23) filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23) lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)
Range generators
std::generator (C++23)
Range adaptor objects
Range adaptor closure objects
range_adaptor_closure (C++23)
Helper items
copyable-box movable-box (until C++23)(C++23)	simple-view non-propagating-cache

 

std::ranges::chunk_view

Member functions
chunk_view::chunk_view (C++23)
chunk_view::base (C++23)
chunk_view::begin (C++23)
chunk_view::end (C++23)
chunk_view::size (C++23)
Classes for input_ranges Deduction guides outer-iterator chunk_view::outer-iterator::outer-iterator (C++23) chunk_view::outer-iterator::operator= (C++23) chunk_view::outer-iterator::operator* (C++23) chunk_view::outer-iterator::operator++ chunk_view::outer-iterator::operator++(int) (C++23)(C++23) operator==(chunk_view::outer-iterator) (C++23) operator-(chunk_view::outer-iterator) (C++23) outer-iterator::value_type chunk_view::outer-iterator::value_type::value_type (C++23)   chunk_view::outer-iterator::value_type::begin (C++23) chunk_view::outer-iterator::value_type::end (C++23) chunk_view::outer-iterator::value_type::size (C++23) inner-iterator chunk_view::inner-iterator::inner-iterator (C++23) chunk_view::inner-iterator::operator= (C++23) chunk_view::inner-iterator::base (C++23) chunk_view::inner-iterator::operator* (C++23) chunk_view::inner-iterator::operator++ chunk_view::inner-iterator::operator++(int) (C++23)(C++23) operator==(chunk_view::inner-iterator) (C++23) operator-(chunk_view::inner-iterator) (C++23) iter_move(chunk_view::inner-iterator) (C++23) iter_swap(chunk_view::inner-iterator) (C++23)	Class template for forward_ranges iterator chunk_view::iterator::iterator (C++23) chunk_view::iterator::base (C++23) chunk_view::iterator::operator* (C++23) chunk_view::iterator::operator[] (C++23) chunk_view::iterator::operator++ chunk_view::iterator::operator++(int) chunk_view::iterator::operator-- chunk_view::iterator::operator--(int) chunk_view::iterator::operator+= chunk_view::iterator::operator-= (C++23)(C++23)(C++23)(C++23)(C++23)(C++23) operator==(chunk_view::iterator) operator<(chunk_view::iterator) operator>(chunk_view::iterator) operator<=(chunk_view::iterator) operator>=(chunk_view::iterator) operator<=>(chunk_view::iterator) (C++23)(C++23)(C++23)(C++23)(C++23)(C++23) operator+(chunk_view::iterator) operator-(chunk_view::iterator) (C++23)(C++23)

 

Defined in header <ranges>
template< ranges::view V >     requires ranges::input_range<V> class chunk_view :     public ranges::view_interface<chunk_view<V>>	(1)	(since C++23)
template< ranges::view V >     requires ranges::forward_range<V> class chunk_view<V> :     public ranges::view_interface<chunk_view<V>>	(2)	(since C++23)
namespace views {     inline constexpr /* unspecified */ chunk = /* unspecified */; }	(3)	(since C++23)
Call signature
template< ranges::viewable_range R > constexpr ranges::view auto chunk( R&& r, ranges::range_difference_t<R> n );		(since C++23)
template< class DifferenceType > constexpr /*range adaptor closure*/ chunk( DifferenceType&& n );		(since C++23)
Helper templates
template< class I > constexpr I __div_ceil( I num, I denom );	(4)	(exposition only*)

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.

1) An implementation that supports the underlying view V that models only input_range.

2) A partial specialization that supports the underlying view V that models forward_range or stronger. Models common_range if the underlying view V is forward_range, common_range, and either sized_range or non bidirectional_range.

3) The name views::chunk denotes a RangeAdaptorObject. Given subexpressions e and n, the expression views::chunk(e, n) is expression-equivalent to chunk_view(e, n).

4) Computes the smallest integer value that is not less than the quotient of dividing num by denom. Equivalent to:

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

Data members

Typical implementations of chunk_view (1,2) hold two non-static data members:

• the underlying view of type V (shown here as base_ for exposition only),
• the "chunk size" of type ranges::range_difference_t<V> (shown here as n_ for exposition only).

In addition, if V models exactly the input_range, chunk_view (1) typically holds two more non-static data members:

• the number of elements left in the current chunk ranges::range_difference_t<V> (shown here as remainder_ for exposition only),
• the current cached underlying iterator __non_propagating_cache<ranges::iterator_t<V>> (shown here as current_ for exposition only).

Member functions

(constructor) (C++23)	constructs a chunk_view (public member function)
base (C++23)	returns a copy of the underlying (adapted) view (public member function)
begin (C++23)	returns an iterator to the beginning (public member function)
end (C++23)	returns an iterator or a sentinel to the end (public member function)
size (C++23)	returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range. (public member function)
Inherited from std::ranges::view_interface
empty (C++20)	returns whether the derived view is empty. Provided if it satisfies sized_range or forward_range. (public member function of std::ranges::view_interface<D>)
cbegin (C++23)	returns a constant iterator to the beginning of the range. (public member function of std::ranges::view_interface<D>)
cend (C++23)	returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D>)
operator bool (C++20)	returns whether the derived view is not empty. Provided if ranges::empty is applicable to it. (public member function of std::ranges::view_interface<D>)
front (C++20)	returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>)
back (C++20)	returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range. (public member function of std::ranges::view_interface<D>)
operator[] (C++20)	returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>)

Nested classes

outer_iterator (C++23)	the output ("chunk-wise") iterator type when V models input_range (1) (exposition-only member class*)
inner_iterator (C++23)	the inner ("element-wise") iterator type when V models input_range (1) (exposition-only member class*)
iterator (C++23)	the iterator type when V models forward_range (2) (exposition-only member class template*)

Helper templates

template< class V > inline constexpr bool ranges::enable_borrowed_range<chunk_view<V>> =     ranges::forward_range<V> && ranges::enable_borrowed_range<V>;		(since C++23)

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.

Feature-test macro	Value	Std	Comment
__cpp_lib_ranges_chunk	202202L	(C++23)	std::ranges::chunk_view

Example

Run this code

#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';
    }
}

Output:

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

• C++23 standard (ISO/IEC 14882:2023):

• 26.7.28 Chunk view [range.chunk]

See also

ranges::chunk_by_viewviews::chunk_by (C++23)	splits the view into subranges between each pair of adjacent elements for which the given predicate returns false (class template) (range adaptor object)
ranges::adjacent_viewviews::adjacent (C++23)	a view consisting of tuples of references to adjacent elements of the adapted view (class template) (range adaptor object)
ranges::slide_viewviews::slide (C++23)	a view whose Mth element is a view over the Mth through (M + N - 1)th elements of another view (class template) (range adaptor object)