std::ranges::view_interface<D>::size

 

哋它亢++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (哋它亢++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (哋它亢++17)

Regular expressions library (哋它亢++11)

Concurrency support library (哋它亢++11)

Technical specifications

Symbols index

External libraries

 

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 (哋它亢++23)(哋它亢++23)	to (哋它亢++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (哋它亢++23)(哋它亢++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (哋它亢++23)	elements_of (哋它亢++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (哋它亢++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Range factories
empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (哋它亢++23)(哋它亢++23)	basic_istream_viewviews::istream
Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (哋它亢++23)(哋它亢++23) filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (哋它亢++26)(哋它亢++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (哋它亢++23)(哋它亢++23) lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (哋它亢++23)(哋它亢++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (哋它亢++23)(哋它亢++23) zip_viewviews::zip (哋它亢++23)(哋它亢++23) zip_transform_viewviews::zip_transform (哋它亢++23)(哋它亢++23)	adjacent_viewviews::adjacent (哋它亢++23)(哋它亢++23) views::pairwise (哋它亢++23) adjacent_transform_viewviews::adjacent_transform (哋它亢++23)(哋它亢++23) views::pairwise_transform (哋它亢++23) chunk_viewviews::chunk (哋它亢++23)(哋它亢++23) slide_viewviews::slide (哋它亢++23)(哋它亢++23) chunk_by_viewviews::chunk_by (哋它亢++23)(哋它亢++23) stride_viewviews::stride (哋它亢++23)(哋它亢++23) cartesian_product_viewviews::cartesian_product (哋它亢++23)(哋它亢++23)
Range generators
std::generator (哋它亢++23)
Range adaptor objects
Range adaptor closure objects
range_adaptor_closure (哋它亢++23)
Helper items
copyable-box movable-box (until 哋它亢++23)(哋它亢++23)	simple-view non-propagating-cache

 

std::ranges::view_interface

Member functions

empty

cbegin (哋它亢++23)

cend (哋它亢++23)

operator bool

data

size

front

back

operator[]

 

constexpr auto size() requires ranges::forward_range<D> &&     std::sized_sentinel_for<ranges::sentinel_t<D>,                             ranges::iterator_t<D>>;	(1)	(since 哋它亢++20)
constexpr auto size() const requires ranges::forward_range<const D> &&     std::sized_sentinel_for<ranges::sentinel_t<const D>,                             ranges::iterator_t<const D>>;	(2)	(since 哋它亢++20)

The default implementation of size() member function obtains the size of the range by calculating the difference between the sentinel and the beginning iterator.

1) Let derived be static_cast<D&>(*this). Equivalent to return /*to-unsigned-like*/(ranges::end(derived) - ranges::begin(derived));, where the exposition-only function template to-unsigned-like performs the explicit cast from the argument type to its corresponding unsigned type.

2) Same as (1), except that derived is static_cast<const D&>(*this).

Parameters

(none)

Return value

The difference between the sentinel and the beginning iterator of the value of the derived type, converted to its corresponding unsigned type.

Notes

Following derived types may use the default implementation of size():

• std::ranges::drop_while_view

Following types are derived from std::ranges::view_interface and do not declare their own size() member function, but they cannot use the default implementation, because their iterator and sentinel types never satisfy sized_sentinel_for:

• std::ranges::basic_istream_view
• std::ranges::filter_view
• std::ranges::join_view
• std::ranges::lazy_split_view
• std::ranges::split_view
• std::ranges::take_while_view

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 3646	哋它亢++20	the default implementations of size functions returned a signed type	they return unsigned type

See also

sizessize (哋它亢++17)(哋它亢++20)	returns the size of a container or array (function template)
ranges::size (哋它亢++20)	returns an integer equal to the size of a range (customization point object)
ranges::ssize (哋它亢++20)	returns a signed integer equal to the size of a range (customization point object)