std:: contiguous_iterator

Defined in header <iterator>
template < class I > concept contiguous_iterator = std:: random_access_iterator < I > && std:: derived_from < /*ITER_CONCEPT*/ < I > , std:: contiguous_iterator_tag > && std:: is_lvalue_reference_v < std:: iter_reference_t < I >> && std:: same_as < std:: iter_value_t < I > , std:: remove_cvref_t < std:: iter_reference_t < I >> > && requires ( const I & i ) { { std:: to_address ( i ) } - > std:: same_as < std:: add_pointer_t < std:: iter_reference_t < I >>> ; } ;		(since C++20)

The contiguous_iterator concept refines random_access_iterator by providing a guarantee the denoted elements are stored contiguously in the memory.

Iterator concept determination

Definition of this concept is specified via an exposition-only alias template /*ITER_CONCEPT*/ .

In order to determine /*ITER_CONCEPT*/ < I > , let ITER_TRAITS < I > denote I if the specialization std:: iterator_traits < I > is generated from the primary template, or std:: iterator_traits < I > otherwise:

• If ITER_TRAITS < I > :: iterator_concept is valid and names a type, /*ITER_CONCEPT*/ < I > denotes the type.
• Otherwise, if ITER_TRAITS < I > :: iterator_category is valid and names a type, /*ITER_CONCEPT*/ < I > denotes the type.
• Otherwise, if std:: iterator_traits < I > is generated from the primary template, /*ITER_CONCEPT*/ < I > denotes std::random_access_iterator_tag .
• Otherwise, /*ITER_CONCEPT*/ < I > does not denote a type and results in a substitution failure.

Semantic requirements

Let a and b be dereferenceable iterators and c be a non-dereferenceable iterator of type I such that b is reachable from a and c is reachable from b . The type I models contiguous_iterator only if all the concepts it subsumes are modeled and:

• std:: to_address ( a ) == std:: addressof ( * a ) ,
• std:: to_address ( b ) == std:: to_address ( a ) + std:: iter_difference_t < I > ( b - a ) , and
• std:: to_address ( c ) == std:: to_address ( a ) + std:: iter_difference_t < I > ( c - a ) .

Equality preservation

Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise).

Implicit expression variations

A requires expression that uses an expression that is non-modifying for some constant lvalue operand also requires implicit expression variations .

Notes

contiguous_iterator is modeled by every pointer type to complete object type.

Iterator types in the standard library that are required to satisfy the LegacyContiguousIterator requirements in C++17 are also required to model contiguous_iterator in C++20.

See also

random_access_iterator (C++20)

specifies that a bidirectional_iterator is a random-access iterator, supporting advancement in constant time and subscripting (concept)