std::contiguous_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>>>;
        };

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