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

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< cpp‎ | ranges
 
 
Ranges library
Range access
Range conversions
(C++23)
Range primitives



Dangling iterator handling
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Adaptors
Range adaptor objects
Range adaptor closure objects
Helper items
 
 
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<V> n );
(since C++23)
template< ranges::forward_range V >

    requires ranges::view<V>

constexpr __range_adaptor_closure slide( ranges::range_difference_t<V> n );
(since C++23)
Helper concepts
template< class V >

concept __slide_caches_nothing =                          // exposition only

    ranges::random_access_range<V> && ranges::sized_range<V>;
(3) (since C++23)
template< class V >

concept __slide_caches_last =                             // exposition only
    !__slide_caches_nothing<V> &&

    ranges::bidirectional_range<V> && ranges::common_range<V>;
(4) (since C++23)
template< class V >

concept __slide_caches_first =                            // exposition only

    !__slide_caches_nothing<V> && !__slide_caches_last<V>;
(5) (since C++23)
Helper templates
1) slide_view is a range adaptor that takes a view and a number n and produces a view whose mth element (a "window") is a view over the mth 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 the 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.

Contents

[edit] Expression-equivalent

Expression e is expression-equivalent to expression f, if

  • e and f have the same effects, and
  • either both are constant subexpressions or else neither is a constant subexpression, and
  • either both are potentially-throwing or else neither is potentially-throwing (i.e. noexcept(e) == noexcept(f)).

[edit] Data members

Typical implementations of slide_view hold from two to four non-static data members:

  • the underlying view of type V (shown here as base_ for exposition only),
  • the "window size" of type ranges::range_difference_t<V> (shown here as n_ for exposition only).
  • the std::optional-like object (shown here as cached_begin_ for exposition only). May be present only if V models the __slide_caches_first helper concept (4).
  • the std::optional-like object (shown here as cached_end_ for exposition only). May be present only if V models the __slide_caches_last helper concept (5).

[edit] Member functions

constructs a slide_view
(public member function) [edit]
(C++23)
returns an iterator to the beginning
(public member function) [edit]
(C++23)
returns an iterator or a sentinel to the end
(public member function) [edit]
(C++23)
returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range.
(public member function) [edit]
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>) [edit]
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>) [edit]
(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>) [edit]
(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>) [edit]
Returns the nth element in the derived view. Provided if it satisfies random_access_range.
(public member function of std::ranges::view_interface<D>) [edit]

[edit] Deduction guides

[edit] 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)

[edit] 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.

[edit] Notes

There is a similarity between ranges::adjacent_view and ranges::slide_view — they both produce a "sliding window" of the size N, and, given a view of the size S, where S >= N > 0, they both will have the same size: S - N + 1. The difference between these view adaptors are:

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

[edit] Example

A link to test: Compiler Explorer.

#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, 1U + v.size()))
    {
        auto const windows = v | std::views::slide(width);
        std::cout << "All sliding windows of width " << width << ": ";
        std::ranges::for_each(windows, print_subrange);
        std::cout << '\n';
    }
}

Output:

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

[edit] References

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

[edit] See also

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