std::ranges::view::counted

namespace view {
    inline constexpr /*unspecified*/ counted = /*unspecified*/;
}

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

#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 << ' ';
}

1 2 3

See also