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std::ranges::views::slide, std::ranges::slide_view

Defined in header <ranges> 
template< ranges::forward_range V >
    requires ranges::view<V>
class slide_view
    : public ranges::view_interface<slide_view<V>>
 (1) (since C++23) 
namespace views {
    inline constexpr /* unspecified */ slide = /* unspecified */;
}
 (2) (since C++23)
Call signature 
template< ranges::viewable_range R >
constexpr ranges::view auto slide( R&& r, ranges::range_difference_t<R> n );
 (since C++23) 
template< class DifferenceType >
constexpr /* range adaptor object */ slide( DifferenceType&& n );
 (since C++23)
Helper concepts 
template< class V >
concept __slide_caches_nothing =
    ranges::random_access_range<V> && ranges::sized_range<V>;
 (3) (exposition only*) 
template< class V >
concept __slide_caches_last =
    !__slide_caches_nothing<V> &&
    ranges::bidirectional_range<V> && ranges::common_range<V>;
 (4) (exposition only*) 
template< class V >
concept __slide_caches_first =
    !__slide_caches_nothing<V> && !__slide_caches_last<V>;
 (5) (exposition only*)
1) slide_view is a range adaptor that takes a view and a number n and produces a view whose m th element (a "window") is a view over the m th through (m + n - 1) th elements of the original view.
Let s be the size of the original view. Then the size of produced view is:
  • s - n + 1, if s >= n,
  • ​0​ otherwise, and the resulting view is empty.
2) The name views::slide denotes a RangeAdaptorObject. Given subexpressions e and n, the expression views::slide(e, n) is expression-equivalent to slide_view(e, n).

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

slide_view always models forward_range, and models bidirectional_range, random_access_range, or sized_range if adapted view type models the corresponding concept.

Data members

Member object Definition
base_ (private) The underlying view of type V.
(exposition-only member object*)
n_ (private) The "window size" of type ranges::range_difference_t<V>.
(exposition-only member object*)
cached_begin_ (private)
(optional)		 An optional-like object. Present only if V models the __slide_caches_first (4).
(exposition-only member object*)
cached_end_ (private)
(optional)		 An optional-like object. Present only if V models the __slide_caches_last (5).
(exposition-only member object*)

Member functions

(C++23)
constructs a slide_view
(public member function)
(C++23)
returns an iterator to the beginning
(public member function)
(C++23)
returns an iterator or a sentinel to the end
(public member function)
(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
(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>)
(C++23)
returns a constant iterator to the beginning of the range.
(public member function of std::ranges::view_interface<D>)
(C++23)
returns a sentinel for the constant iterator of the range.
(public member function of std::ranges::view_interface<D>)
(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>)
(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>)
(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>)
(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>)

Deduction guides

Nested classes

(C++23)
the iterator type
(exposition-only member class template*)
(C++23)
the sentinel type used when slide_view is not a common_range
(exposition-only member class template*)

Helper templates

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

This specialization of ranges::enable_borrowed_range makes slide_view satisfy borrowed_range when the underlying view satisfies it.

Notes

There are similarities between ranges::adjacent_view and ranges::slide_view:

  • Both create a "sliding window" of size N.
  • Both have the same size S - N + 1, where S is the size of an adapted view such that S >= N > 0.

The differences between these adapters are:

View adaptor value_type The window size N
ranges::adjacent_view A std::tuple object A template parameter
ranges::slide_view A range A runtime parameter
Feature-test macro Value Std Feature
__cpp_lib_ranges_slide 202202L (C++23) std::ranges::slide_view

Example

#include <algorithm>
#include <iostream>
#include <ranges>
 
auto print_subrange = [](std::ranges::viewable_range auto&& r)
{
    std::cout << '[';
    for (char space[]{0,0}; auto elem : r)
        std::cout << space << elem, *space = ' ';
    std::cout << "] ";
};
 
int main()
{
    const auto v = {1, 2, 3, 4, 5, 6};
 
    std::cout << "All sliding windows of width:\n";
    for (const unsigned width : std::views::iota(1U, 1U + v.size()))
    {
        auto const windows = v | std::views::slide(width);
        std::cout << "W = " << width << ": ";
        std::ranges::for_each(windows, print_subrange);
        std::cout << '\n';
    }
}

Output:

All sliding windows of width W:
W = 1: [1] [2] [3] [4] [5] [6] 
W = 2: [1 2] [2 3] [3 4] [4 5] [5 6] 
W = 3: [1 2 3] [2 3 4] [3 4 5] [4 5 6] 
W = 4: [1 2 3 4] [2 3 4 5] [3 4 5 6] 
W = 5: [1 2 3 4 5] [2 3 4 5 6] 
W = 6: [1 2 3 4 5 6]

References

  • C++23 standard (ISO/IEC 14882:2023):
    • 26.7.29 Slide view [range.slide]

See also

(C++23)
a view consisting of tuples of references to adjacent elements of the adapted view
(class template) (range adaptor object)
(C++23)
a range of views that are N-sized non-overlapping successive chunks of the elements of another view
(class template) (range adaptor object)

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