std::experimental::ranges::RandomAccessIterator

 

C++

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Concepts library (C++20)

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Technical Specifications

 

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals 2 TS)

Extensions for parallelism (parallelism TS)

Extensions for parallelism 2 (parallelism TS v2)

Extensions for concurrency (concurrency TS)

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Ranges

Concepts

General utilities

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Ranges

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Iterators library

Iterator concepts
Readable Writable WeaklyIncrementable Incrementable	Iterator Sentinel SizedSentinel	InputIterator ForwardIterator BidirectionalIterator RandomAccessIterator	OutputIterator
Indirect callable concepts
IndirectUnaryInvocableIndirectRegularUnaryInvocable	IndirectUnaryPredicate	IndirectRelation	IndirectStrictWeakOrder
Common algorithm requirements
IndirectlyMovable IndirectlyMovableStorable	IndirectlyCopyable IndirectlyCopyableStorable	IndirectlySwappable IndirectlyComparable	Permutable Mergeable Sortable
Concept utilities
indirect_result_of	projected
Iterator utilities and operations
iter_move iter_swap	advance distance	next prev
Iterator traits
difference_type value_type reference_trvalue_reference_titer_common_reference_t iterator_category	input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tag	ranges::iterator_traits std::iterator_traits<InputIterator>std::iterator_traits<OutputIterator>
Iterator adaptors
reverse_iterator move_iterator move_sentinel	back_insert_iterator front_insert_iterator insert_iterator	common_iterator counted_iterator default_sentinel	danglingsafe_iterator_t unreachable
Stream iterators
istream_iterator	ostream_iterator	istreambuf_iterator	ostreambuf_iterator

 

Defined in header <experimental/ranges/iterator>
template <class I> concept bool RandomAccessIterator =   BidirectionalIterator<I> &&   DerivedFrom<ranges::iterator_category_t<I>, ranges::random_access_iterator_tag> &&   StrictTotallyOrdered<I> &&   SizedSentinel<I, I> &&   requires(I i, const I j, const ranges::difference_type_t<I> n) {     { i += n } -> Same<I>&;     { j + n }  -> Same<I>&&;     { n + j }  -> Same<I>&&;     { i -= n } -> Same<I>&;     { j - n }  -> Same<I>&&;     j[n];     requires Same<decltype(j[n]), ranges::reference_t<I>>;   };		(ranges TS)

The concept RandomAccessIterator<I> refines BidirectionalIterator by adding support for constant time advancement with the +=, +, -=, and - operators, constant time computation of distance with -, and array notation with subscripting.

Let a and b be valid iterators of type I such that b is reachable from a, and let n be a value of type ranges::difference_type_t<I> equal to b - a. RandomAccessIterator<I> is satisfied only if:

• (a += n) is equal to b.
• std::addressof(a += n) is equal to std::addressof(a).
• (a + n) is equal to (a += n).
• (a + n) is equal to (n + a).
• For any two positive integers x and y, if a + (x + y) is valid, then a + (x + y) is equal to (a + x) + y.
• a + 0 is equal to a.
• If (a + (n - 1)) is valid, then --b is equal to (a + (n - 1)).
• (b += -n) and (b -= n) are both equal to a.
• std::addressof(b -= n) is equal to std::addressof(b).
• (b - n) is equal to (b -= n).
• If b is dereferenceable, then a[n] is valid and is equal to *b.
• bool(a <= b) is true .

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).

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 only modify 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.