std::ranges::iota_view<W, Bound>::size

 

C++

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Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata 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    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	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 ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (C++26)(C++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	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::iota_view

Member functions

iota_view::iota_view

iota_view::begin

iota_view::end

iota_view::empty

iota_view::size

Deduction guides

Nested classes

Iterator

Helper concepts

decrementable

advanceable

Member types

Member functions

iota_view::iterator::iterator

iota_view::iterator::operator*

iota_view::iterator::operator[]

iota_view::iterator::operator++ iota_view::iterator::operator++(int)

iota_view::iterator::operator-- iota_view::iterator::operator--(int)

iota_view::iterator::operator+=

iota_view::iterator::operator-=

Non-member functions

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

operator+(iota_view::iterator)

operator-(iota_view::iterator)

Sentinel

Member functions

iota_view::sentinel::sentinel

Non-member functions

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

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

 

constexpr auto size() const     requires (std::same_as<W, Bound> && /*advanceable*/<W>) ||              (/*is-integer-like*/<W> && /*is-integer-like*/<Bound>) ||              std::sized_sentinel_for<Bound, W>;		(since C++20)

Returns the size of the view if the view is bounded.

For the definitions of /*advanceable*/ and /*is-integer-like*/, see advanceable and is-integer-like respectively.

Return value

If any of W and Bound is not a integer-like type, returns to-unsigned-like (bound_ - value_ ).

Otherwise, returns (value_ < 0) ?
    (
        (bound_ < 0) ?
            to-unsigned-like (-value_ ) - to-unsigned-like (-bound_ ) :
            to-unsigned-like (bound_ ) + to-unsigned-like (-value_ )
    ) :
    to-unsigned-like (bound_ ) - to-unsigned-like (value_ ) .

Example

Run this code

#include <cassert>
#include <ranges>
 
int main()
{
    unsigned initial_value{1}, bound{5};
    auto i{std::views::iota(initial_value, bound)};
    assert(i.size() == bound - initial_value and i.size() == 4);
 
    auto u{std::views::iota(8)};
    // assert(u.size()); // Error: size() is not present since “u” is unbounded
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3610	C++20	size might reject integer-class types	accept if possible

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)