std::ranges::views::chunk, std::ranges::chunk_view - cppreference.com (original) (raw)

Defined in header
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. 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).

  3. 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;

Contents

[edit] Data members

Member Description
V base_ the underlying view(exposition-only member object*)
ranges::range_difference_t<V> n_ the “chunk” size(exposition-only member object*)

[edit] Member functions

(constructor) constructs a chunk_view (public member function) [edit]
base returns a copy of the underlying (adapted) view (public member function) [edit]
begin returns an iterator to the beginning (public member function) [edit]
end returns an iterator or a sentinel to the end (public member function) [edit]
size returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range (public member function) [edit]
reserve_hint(C++26) returns the approximate size of the resulting approximately_sized_range (public member function) [edit]
Inherited from std::ranges::view_interface
empty returns whether the derived view is empty, provided only if it satisfies sized_range or forward_range (public member function of std::ranges::view_interface) [edit]
cbegin(C++23) returns a constant iterator to the beginning of the range (public member function of std::ranges::view_interface) [edit]
cend(C++23) returns a sentinel for the constant iterator of the range (public member function of std::ranges::view_interface) [edit]
operator bool returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of std::ranges::view_interface) [edit]
front returns the first element in the derived view, provided if it satisfies forward_range (public member function of std::ranges::view_interface) [edit]
back returns the last element in the derived view, provided only if it satisfies bidirectional_range and common_range (public member function of std::ranges::view_interface) [edit]
operator[] returns the nth element in the derived view, provided only if it satisfies random_access_range (public member function of std::ranges::view_interface) [edit]

[edit] Deduction guides

[edit] Nested classes

[edit] 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.

[edit] 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 Feature
__cpp_lib_ranges_chunk 202202L (C++23) std::ranges::chunk_view

[edit] Example

#include #include #include #include   auto print_subrange = 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]

[edit] References

[edit] See also