NAME¶

std::experimental::ranges::value_type - std::experimental::ranges::value_type

Synopsis¶

Defined in header <experimental/ranges/iterator>
template< class I > (1)
struct value_type { };
template< class T > (2)
struct value_type<T*>;
template< class I >

requires std::is_array<I>::value (3)

struct value_type<I> : value_type<std::decay_t<I>> { };
template< class T > (4)
struct value_type<const T> : value_type<std::decay_t<T>> { };
template <class T>

requires requires { typename T::value_type; } (5)

struct value_type<T>;
template <class T>

requires requires { typename T::element_type; } (6)

struct value_type<T>;

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 > (ranges TS)
using value_type_t = typename ranges::value_type<T>::type;

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¶

Readable specifies that a type is readable by applying operator *
(concept)
compatibility traits class that collects an iterator’s associated
iterator_traits types
(alias template)