std::ranges:: sized_range, std::ranges:: disable_sized_range
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Defined in header
<ranges>
|
||
|
template
<
class
T
>
concept sized_range
=
ranges::
range
<
T
>
&&
|
(1) | (since C++20) |
|
template
<
class
>
constexpr bool disable_sized_range = false ; |
(2) | (since C++20) |
sized_range
concept specifies the requirements of a
range
type that knows its size in constant time with the
size
function.
disable_sized_range
exists to allow use of range types that provide a
size
function (either as a member or as a non-member) but do not in fact model
sized_range
. Users may specialize
disable_sized_range
for cv-unqualified program-defined types. Such specializations shall be usable in
constant expressions
and have type
const
bool
.
Semantic requirements
t
of type
std::
remove_reference_t
<
T
>
,
T
models
sized_range
only if
- ranges:: size ( t )
-
- has amortized constant-time complexity,
-
does not alter the value of
tin a manner observable to equality-preserving expressions, and - is equal to ranges:: distance ( ranges:: begin ( t ) , ranges:: end ( t ) ) , and
-
if
ranges::
iterator_t
<
T
>
models
forward_iterator, ranges:: size ( t ) is well-defined regardless of the evaluation of ranges:: begin ( t ) (in other words, a single-pass sized range may support a call to size only before the first call to begin, but a forward range must support size at all times).
Notes
disable_sized_range
cannot be used to opt-out a range whose iterator and sentinel satisfy
sized_sentinel_for
;
std::disable_sized_sentinel_for
must be used instead.
disable_sized_range
cannot be specialized for array types or reference types.
Example
#include <forward_list> #include <list> #include <ranges> static_assert ( std::ranges::sized_range<std::list<int>> and not std::ranges::sized_range<std::forward_list<int>> ); int main() {}
See also
|
(C++20)
|
specifies a range whose iterator type satisfies
random_access_iterator
(concept) |
|
(C++20)
|
specifies a range whose iterator type satisfies
contiguous_iterator
(concept) |