std::experimental::ranges::value_type
From cppreference.com
< cpp | experimental | ranges
Defined in header <experimental/ranges/iterator>
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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
.Contents |
[edit] Helper alias template
template< class T > using value_type_t = typename ranges::value_type<T>::type; |
(ranges TS) | |
[edit] 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.
[edit] Example
This section is incomplete Reason: no example |
[edit] See also
specifies that a type is readable by applying operator * (concept) | |
compatibility traits class that collects an iterator’s associated types (alias template) |