std::ranges::view_interface<D>::size
|
constexpr
auto size(
) requires ranges::forward_range
<D>
&&
std::sized_sentinel_for
<
ranges::sentinel_t
<D>, |
(1) | (since C++20) |
|
constexpr
auto size(
)
const requires ranges::forward_range
<
const D>
&&
std::sized_sentinel_for
<
ranges::sentinel_t
<
const D>, |
(2) | (since C++20) |
The default implementation of size() member function obtains the size of the range by calculating the difference between the sentinel and the beginning iterator.
Return value
to-unsigned-like
(
ranges::end
(
static_cast
<D&
>
(this)
)
-
to-unsigned-like
(
ranges::end
(
static_cast
<
const D&
>
(this)
)
-
Notes
Following derived types may use the default implementation of size():
Following types are derived from std::ranges::view_interface and do not declare their own size() member function, but they cannot use the default implementation, because their iterator and sentinel types never satisfy sized_sentinel_for
- std::ranges::basic_istream_view
- std::ranges::filter_view
- std::ranges::join_view
- std::ranges::lazy_split_view
- std::ranges::split_view
- std::ranges::take_while_view
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 3646 | C++20 | the default implementations of size functions returned a signed type
|
they return unsigned type |
See also
|
(C++17)(C++20)
|
returns the size of a container or array (function template) |
|
(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) |