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std::readable_traits

From cppreference.com
< cpp‎ | iterator
 
 
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Defined in header <iterator>
template< class I >
struct readable_traits { };
(1) (since C++20)
template< class T >
struct readable_traits<T*>;
(2) (since C++20)
template< class I >

  requires std::is_array_v<I>

struct readable_traits<I>;
(3) (since C++20)
template< class T >
struct readable_traits<const T> : value_type<T> { };
(4) (since C++20)
template <class T>

  requires requires { typename T::value_type; }

struct readable_traits<T>;
(5) (since C++20)
template <class T>

  requires requires { typename T::element_type; }

struct readable_traits<T>;
(6) (since C++20)

Computes the associated value type of the type I, if any. Users may specialize readable_traits 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 value_type equal to std::remove_cv_t<T>. Otherwise, there is no member value_type.
3) Specialization for array types. Provides a member type value_type equal to std::remove_cv_t<std::remove_extent_t<I>>.
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 value_type equal to std::remove_cv_t<typename T::value_type>. Otherwise, there is no member value_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 value_type equal to std::remove_cv_t<typename T::element_type>. Otherwise, there is no member value_type.

[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

[edit] See also

specifies that a type is readable by applying operator *
(concept) [edit]
computes the associate types of an iterator
(alias template) [edit]
provides uniform interface to the properties of an iterator
(class template) [edit]