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std::ranges::views::stride, std::ranges::stride_view - cppreference.com

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Defined in header <ranges>

template< ranges::input_range V > requires ranges::view<V> class stride_view : public ranges::view_interface<stride_view<V>>

 (1) (since C++23)

namespace views { inline constexpr /* unspecified */ stride = /* unspecified */; }

 (2) (since C++23)

Call signature

template< ranges::viewable_range R > constexpr ranges::view auto stride( R&& r, ranges::range_difference_t<R> n );

 (since C++23)

template< class DifferenceType > constexpr /*range adaptor closure*/ stride( DifferenceType&& n );

 (since C++23)

Helper templates

1) stride_view is a range adaptor that takes a view and a number n and produces a view, that consists of elements of the original view by advancing over n elements at a time. This means that each mth element of the produced view is (n * i)th element of the original view, for some non-negative index i. The elements of the original view, whose “index” is not a multiple of n, are not present in the produced view.

Let S be the size of the original view. Then the size of produced view is:

  • (S / n) + (S % n ? 1 : 0), if S >= n; otherwise,
  • 1, if S > 0; otherwise,
  • 0, and the resulting view is empty.

2) The name views::stride denotes a RangeAdaptorObject. Given subexpressions e and n, the expression views::stride(e, n) is expression-equivalent to stride_view(e, n).

The n must be greater than 0, otherwise the behavior is undefined.

stride_view always models input_range, and models forward_range, bidirectional_range, random_access_range, and/or sized_range, if adapted view type V models the corresponding concept. stride_view<V> models common_range whenever the underlying view V does.

Data members

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

Member functions

constructs a stride_view
(public member function) [edit]

(C++23)

 returns the stored stride value
(public member function)
returns a copy of the underlying (adapted) view
(public member function) [edit]
returns an iterator to the beginning
(public member function) [edit]
returns an iterator or a sentinel to the end
(public member function) [edit]
returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range
(public member function) [edit]
returns the approximate size of the resulting approximately_sized_range
(public member function) [edit]
Inherited from ranges::view_interface
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<D>) [edit]

(C++23)

 returns a constant iterator to the beginning of the range
(public member function of std::ranges::view_interface<D>) [edit]

(C++23)

 returns a sentinel for the constant iterator of the range
(public member function of std::ranges::view_interface<D>) [edit]
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<D>) [edit]
returns the first element in the derived view, provided if it satisfies forward_range
(public member function of std::ranges::view_interface<D>) [edit]
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<D>) [edit]
returns the nth element in the derived view, provided only if it satisfies random_access_range
(public member function of std::ranges::view_interface<D>) [edit]

Deduction guides

Nested classes

the iterator type
(exposition-only member class template*)

Helper templates

template< class V > constexpr bool ranges::enable_borrowed_range<stride_view<V>> = ranges::enable_borrowed_range<V>;

 (since C++23)

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

Notes

Feature-test macro Value Std Feature
__cpp_lib_ranges_stride 202207L (C++23) std::ranges::stride_view

Example

#include <algorithm>
#include <iostream>
#include <ranges>
#include <string_view>
using namespace std::literals;

void print(std::ranges::viewable_range auto&& v, std::string_view separator = " ")
{
    for (auto const& x : v)
        std::cout << x << separator;
    std::cout << '\n';
}

int main()
{
    print(std::views::iota(1, 13) | std::views::stride(3));
    print(std::views::iota(1, 13) | std::views::stride(3) | std::views::reverse);
    print(std::views::iota(1, 13) | std::views::reverse | std::views::stride(3));

    print("0x0!133713337*x//42/A$@"sv | std::views::stride(0B11) |
          std::views::transform([](char O) -> char { return 0100 | O; }),
          "");
}

Output: 

1 4 7 10
10 7 4 1
12 9 6 3
password

References

  • C++23 standard (ISO/IEC 14882:2024):
  • 26.7.31 Stride view [range.stride]

See also