std::ranges::view::counted (3) - Linux Manuals

std::ranges::view::counted: std::ranges::view::counted


std::ranges::view::counted - std::ranges::view::counted


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.


// 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 << ' ';


  1 2 3

See also

                 combines an iterator-sentinel pair into a View
subrange (class template)

counted_iterator iterator adaptor that tracks the distance to the end of the range
                 (class template)