std::indirectly_readable_traits(3)

NAME
std::indirectly_readable_traits - std::indirectly_readable_traits

Synopsis
   Defined in header <iterator>
   template< class I > (1) (since C++20)
   struct indirectly_readable_traits { };
   template< class T > (2) (since C++20)
   struct indirectly_readable_traits<T*>;
   template< class I >
   requires std::is_array_v<I> (3) (since C++20)
   struct indirectly_readable_traits<I>;
   template< class T >
   struct indirectly_readable_traits<const T> : (4) (since C++20)
   indirectly_readable_traits<T> { };
   template </*has-member-value-type*/ T> (5) (since C++20)
   struct indirectly_readable_traits<T>;
   template </*has-member-element-type*/ T> (6) (since C++20)
   struct indirectly_readable_traits<T>;
   template </*has-member-value-type*/ T>
   requires /*has-member-element-type*/<T> (7) (since C++20)
   struct indirectly_readable_traits<T> { };
   template </*has-member-value-type*/ T>
   requires /*has-member-element-type*/<T> &&
   std::same_as<std::remove_cv_t<typename T::element_type>, (8) (since C++20)
   std::remove_cv_t<typename T::value_type>>
   struct indirectly_readable_traits<T>;
   Computes the associated value type of the type I, if any. Users may specialize
   indirectly_readable_traits for a program-defined type.
   1) Primary template has no member value_type.
   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 (e.g., std::reverse_iterator). 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.
   7-8) Specialization for types that define public and accessible member types
   value_type and element_type (e.g., std::span). If both T::value_type and
   T::element_type are object types and they become the same type after removing
   cv-qualifiers on the top-level, provides a member type value_type equal to
   std::remove_cv_t<typename T::value_type>. Otherwise, there is no member value_type.

Notes
   value_type is intended for use with indirectly_readable types such as iterators. It
   is not intended for use with ranges.

Example
    This section is incomplete
    Reason: no example
  Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
                       specializations were ambiguous for
   LWG 3446 C++20 types containing a disambiguating
                       both value_type and element_type specialization added
                       member types
                       LWG 3446 introduced hard error for
   LWG 3541 C++20 ambiguous cases that made resulting substitution
                       value_type and element_type are failure
                       different

See also
   indirectly_readable specifies that a type is indirectly readable by applying
   (C++20) operator *
                        (concept)
   iter_value_t
   iter_reference_t
   iter_const_reference_t
   iter_difference_t
   iter_rvalue_reference_t
   iter_common_reference_t computes the associated types of an iterator
   (C++20) (alias template)
   (C++20)
   (C++23)
   (C++20)
   (C++20)
   (C++20)
   iterator_traits provides uniform interface to the properties of an iterator
                        (class template)