std::contiguous_iterator

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

[edit] 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 .
  (That is, std::derived_from </*ITER_CONCEPT*/<I>, std::contiguous_iterator_tag > is assumed to be false.)
• Otherwise, /*ITER_CONCEPT*/<I> does not denote a type and results in a substitution failure.

[edit] 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 all following conditions are satisfied:

• std::to_address (a) == std::addressof (*a).
• std::to_address (b) == std::to_address (a) + std::iter_difference_t <I>(b - a).
• std::to_address (c) == std::to_address (a) + std::iter_difference_t <I>(c - a).
• std::to_address (I{}) is well-defined.
• ranges::iter_move (a) has the same type, value category, and effects as std::move(*a).
• If ranges::iter_swap (a, b) is well-formed, it has effects equivalent to ranges::swap (*a, *b).

[edit] Equality preservation

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

[edit] Implicit expression variations

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

[edit] 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.

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also