std::ranges::iota_view<W, Bound>::size
| constexpr auto size() const requires (std::same_as<W, Bound> && /*advanceable*/<W>) || |
(since C++20) | |
Returns the size of the view if the view is bounded.
For the definitions of /*advanceable*/ and /*is-integer-like*/, see advanceable and is-integer-like respectively.
Return value
If any of W and Bound is not a integer-like type, returns to-unsigned-like (bound_ - value_ ).
Otherwise, returns
(value_ < 0) ?
(
(bound_ < 0) ?
to-unsigned-like (-value_ ) - to-unsigned-like (-bound_ ) :
to-unsigned-like (bound_ ) + to-unsigned-like (-value_ )
) :
to-unsigned-like (bound_ ) - to-unsigned-like (value_ )
.
Example
#include <cassert> #include <ranges> int main() { unsigned initial_value{1}, bound{5}; auto i{std::views::iota(initial_value, bound)}; assert(i.size() == bound - initial_value and i.size() == 4); auto u{std::views::iota(8)}; // assert(u.size()); // Error: size() is not present since “u” is unbounded }
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3610 | C++20 | size might reject integer-class types
|
accept if possible |
See also
| (C++20) |
returns an integer equal to the size of a range (customization point object) |
| (C++20) |
returns a signed integer equal to the size of a range (customization point object) |