std::indirectly_readable_traits

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (deprecated in C++17)	incrementable_traits (C++20) indirectly_readable_traits (C++20) iter_value_titer_difference_titer_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++20)(C++20)
Algorithm concepts and utilities
Indirect callable concepts
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20) indirect_unary_predicate (C++20)	indirect_binary_predicate (C++20) indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20) indirectly_copyable_storable (C++20)	indirectly_swappable (C++20) indirectly_comparable (C++20) permutable (C++20) mergeable (C++20) sortable (C++20)
Utilities
indirect_result_t	projected
Iterator adaptors
reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) back_inserter front_inserter inserter
Stream iterators
istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
Iterator customization points
ranges::iter_move (C++20)
ranges::iter_swap (C++20)
Iterator operations
advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
Range access
begincbegin (C++11)(C++14) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

Defined in header <iterator>
template< class I > struct indirectly_readable_traits { };	(1)	(since C++20)
template< class T > struct indirectly_readable_traits<T*>;	(2)	(since C++20)
template< class I >   requires std::is_array_v<I> struct indirectly_readable_traits<I>;	(3)	(since C++20)
template< class T > struct indirectly_readable_traits<const T> : indirectly_readable_traits<T> { };	(4)	(since C++20)
template <class T>   requires requires { typename T::value_type; } struct indirectly_readable_traits<T>;	(5)	(since C++20)
template <class T>   requires requires { typename T::element_type; } struct indirectly_readable_traits<T>;	(6)	(since C++20)

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 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.

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

See also

indirectly_readable (C++20)	specifies that a type is indirectly readable by applying operator * (concept)
iter_value_titer_reference_titer_difference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++20)(C++20)	computes the associate types of an iterator (alias template)
iterator_traits	provides uniform interface to the properties of an iterator (class template)