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) | |
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template
<
class T >
struct value_type<T* > ; |
(2) | |
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template
<
class I >
requires std::is_array<I>::value |
(3) | |
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template
<
class T >
struct value_type< const T> : value_type< std::decay_t <T>> { } ; |
(4) | |
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template
<
class T >
requires requires { typename T::value_type; } |
(5) | |
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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
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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) |
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| compatibility traits class that collects an iterator’s associated types (alias template) |