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
modelsIterator
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) |