# std::ranges::view::counted

From cppreference.com

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}

- if T models
- 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

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

(C++20) |
iterator adaptor that tracks the distance to the end of the range (class template) |