std::experimental::ranges::value_type
< cpp | experimental | ranges
|
Defined in header
<experimental/ranges/iterator> |
||
|
template< class I >
struct value_type {}; |
(1) | |
|
template< class T >
struct value_type<T*>; |
(2) | |
|
template< class I >
requires std::is_array<I>::value |
(3) | |
|
template< class T >
struct value_type<const T> : value_type<std::decay_t<T>> {}; |
(4) | |
|
template< class T >
requires requires { typename T::value_type; } |
(5) | |
|
template< class T >
requires requires { typename T::element_type; } |
(6) | |
Computes the associated value type of the type I, if any. Users may specialize value_type for a program-defined type.
1) Primary template is an empty struct.
2) Specialization for pointers. If
T is an object type, provides a member type type equal to std::remove_cv_t<T>. Otherwise, there is no member type.3) Specialization for array types.
4) Specialization for const-qualified types.
5) Specialization for types that define a public and accessible member type
value_type. If T::value_type is an object type, provides a member type type equal to T::value_type. Otherwise, there is no member type.6) Specialization for types that define a public and accessible member type
element_type (e.g., std::shared_ptr). If T::element_type is an object type, provides a member type type equal to std::remove_cv_t<typename T::element_type>. Otherwise, there is no member type.Helper alias template
|
template< class T >
using value_type_t = typename ranges::value_type<T>::type; |
(ranges TS) | |
Notes
If a type contains both a value_type member and a element_type member, then the specializations (5) and (6) are ambiguous.
value_type is intended for use with Readable types such as iterators. It is not intended for use with ranges.
Example
| This section is incomplete Reason: no example |
See also
specifies that a type is readable by applying operator *(concept) |
|
| compatibility traits class that collects an iterator’s associated types (alias template) |