std::ranges::view::counted

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Ranges library

Range access
begincbegin endcend	rbegincrbegin rendcrend	size empty datacdata
Range primitives
iterator_t	sentinel_t
Dangling iterator handling
dangling	safe_iterator_t	safe_subrange_t
Range concepts
Range SizedRange View	InputRange OutputRange ForwardRange	BidirectionalRange RandomAccessRange ContiguousRange	CommonRange ViewableRange
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewview::empty	single_viewview::single	iota_viewview::iota	view::counted
Adaptors
all_viewview::all ref_view filter_viewview::filter	transform_viewview::transform                                take_viewview::take	join_viewview::join split_viewview::split	common_viewview::common reverse_viewview::reverse

 

namespace view {     inline constexpr /*unspecified*/ counted = /*unspecified*/; }		(since C++20)

A counted view presents a View of the elements of the counted range [i, n) for some iterator i and non-negative integer n.

A counted range [i, n) is the n elements starting with the element pointed to by i and up to but not including the element, if any, pointed to by the result of n applications of ++i.

If n == 0, the counted range is valid and empty. Otherwise, the counted range is only valid if n is positive, i is dereferenceable, and [++i, --n) is a valid counted range.

Formally, if E and F are expressions, and T is the type std::decay_t<decltype((E))>, then

if T models Iterator and decltype((F)) models ConvertibleTo<iter_difference_t<T>>,

if T models RandomAccessIterator, view::counted(E, F) is expression-equivalent to ranges::subrange{E, E + static_cast<std::iter_difference_t<T>>(F)}

otherwise view::counted(E, F) is expression-equivalent to ranges::subrange{std::counted_iterator{E, F}, std::default_sentinel}

otherwise, view::counted(E, F) is ill-formed.

Example

Run this code

#include <ranges>
#include <iostream>
 
int main()
{
  int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
  for(int i : std::view::counted(a, 3))
    std::cout << i << ' ';
}

Output:

1 2 3

See also

subrange	combines an iterator-sentinel pair into a View (class template)
counted_iterator (C++20)	iterator adaptor that tracks the distance to the end of the range (class template)