Difference between revisions of "cpp/iterator/contiguous iterator"
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{{ddcl|header=iterator|since=c++20|1= | {{ddcl|header=iterator|since=c++20|1= | ||
| − | template<class I> | + | 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>>>; | |
| − | + | }; | |
}} | }} | ||
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===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/iterator/dsc | + | {{dsc inc|cpp/iterator/dsc random_access_iterator}} |
{{dsc end}} | {{dsc end}} | ||
| − | {{langlinks|es|ja|ru|zh}} | + | {{langlinks|de|es|ja|ru|zh}} |
Latest revision as of 04:47, 29 September 2023
| Defined in header <iterator>
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| template< class I > concept contiguous_iterator = |
(since C++20) | |
The contiguous_iterator concept refines random_access_iterator by providing a guarantee the denoted elements are stored contiguously in the memory.
Contents |
[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.
- 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:
- 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).
[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] See also
| (C++20) |
specifies that a bidirectional_iterator is a random-access iterator, supporting advancement in constant time and subscripting (concept) |
