std::ranges::slide_view<V>::size

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted as_input_viewviews::as_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view 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 closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::slide_view

Member functions

slide_view::slide_view

slide_view::begin

slide_view::end

slide_view::size

slide_view::reserve_hint (C++26)

Deduction guides

Iterator

Member functions

slide_view::iterator::iterator

slide_view::iterator::operator*

slide_view::iterator::operator[]

slide_view::iterator::operator++ slide_view::iterator::operator++(int) slide_view::iterator::operator-- slide_view::iterator::operator--(int) slide_view::iterator::operator+= slide_view::iterator::operator-=

Non-member functions

operator==(slide_view::iterator) operator<(slide_view::iterator) operator>(slide_view::iterator) operator<=(slide_view::iterator) operator>=(slide_view::iterator) operator<=>(slide_view::iterator)

operator+(slide_view::iterator) operator-(slide_view::iterator)

Sentinel

Member functions

slide_view::sentinel::sentinel

Non-member functions

operator==(slide_view::iterator,slide_view::sentinel)

operator-(slide_view::iterator,slide_view::sentinel)

 

constexpr auto size() requires ranges::sized_range<V>;	(1)	(since C++23)
constexpr auto size() const requires ranges::sized_range<const V>;	(2)	(since C++23)

See More

Returns the number of elements.

Let base_ and n_ be the underlying view and “window size” respectively. Equivalent to

auto sz = ranges::distance(base_) - n_ + 1;
if (sz < 0)
    sz = 0;
return /*to-unsigned-like*/(sz);

Return value

The number of elements. Equals to 0, if the number of elements (ranges::size(base_)) in underlying view base_ is less than “window size” n_.

Example

Run this code

#include <forward_list>
#include <iostream>
#include <list>
#include <ranges>

int main()
{
    constexpr static auto v = {1, 2, 3, 4, 5, 6};

    constexpr int width1{4};
    constexpr auto view1{std::views::slide(v, width1)};
    static_assert(view1.size() == 3);
    static_assert(view1.size() == (v.size() - width1 + 1));

    constexpr int width2{8};
    constexpr auto view2{std::views::slide(v, width2)};
    // window is too wide, so view2 has no elements:
    static_assert(view2.size() == 0);

    std::forward_list forward_list = v;
    const auto view3{std::views::slide(forward_list, width1)};
//  auto x = view3.size(); // error: sized_range constraint is not satisfied

    std::list list = v;
    const auto view4{std::views::slide(list, width1)};
    std::cout << view4.size() << '\n'; // prints 3
}

Output:

3

See also

ranges::size (C++20)	returns an integer equal to the size of a range (customization point object)
ranges::ssize (C++20)	returns a signed integer equal to the size of a range (customization point object)