std::contiguous_iterator(3)

NAME
std::contiguous_iterator - std::contiguous_iterator

Synopsis
   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< (since
   std::iter_value_t<I>, std::remove_cvref_t<std::iter_reference_t<I>> C++20)
   > &&
   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
   An expression is equality preserving if it results in equal outputs given equal
   inputs.
     * The inputs to an expression consist of its operands.
     * The outputs of an expression consist of its result and all operands modified by
       the expression (if any).
   In specification of standard concepts, operands are defined as the largest
   subexpressions that include only:
     * an id-expression, and
     * invocations of std::move, std::forward, and std::declval.
   The cv-qualification and value category of each operand is determined by assuming
   that each template type parameter denotes a cv-unqualified complete non-array object
   type.
   Every expression required to be equality preserving is further required to be
   stable: two evaluations of such an expression with the same input objects must have
   equal outputs absent any explicit intervening modification of those input objects.
   Unless noted otherwise, every expression used in a requires-expression is required
   to be equality preserving and stable, and the evaluation of the expression may
   modify only its non-constant operands. Operands that are constant must not be
   modified.
  Implicit expression variations
   A requires-expression that uses an expression that is non-modifying for some
   constant lvalue operand also implicitly requires additional variations of that
   expression that accept a non-constant lvalue or (possibly constant) rvalue for the
   given operand unless such an expression variation is explicitly required with
   differing semantics. These implicit expression variations must meet the same
   semantic requirements of the declared expression. The extent to which an
   implementation validates the syntax of the variations is unspecified.

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
                        specifies that a bidirectional_iterator is a random-access
   random_access_iterator iterator, supporting advancement in constant time and
   (C++20) subscripting
                        (concept)