std::experimental::ranges::BidirectionalIterator

C++

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Technical Specifications

Technical specifications

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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_t rvalue_reference_t iter_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
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istream_iterator	ostream_iterator	istreambuf_iterator	ostreambuf_iterator

Defined in header <experimental/ranges/iterator>
template < class I > concept bool BidirectionalIterator = ForwardIterator<I> && DerivedFrom<ranges::iterator_category_t<I>, ranges::bidirectional_iterator_tag> && requires(I i) { { --i } -> Same<I>&; { i-- } -> Same<I>&&; };		(ranges TS)

The concept BidirectionalIterator<I> refines ForwardIterator by adding the ability to move an iterator backward.

A bidirectional iterator r is said to be decrementable if and only if there exists some s such that ++s == r. All decrementable iterators r shall be in the domain of the expressions --r and r--.

Let a and b be decrementable objects of type I. BidirectionalIterator<I> is satisfied only if:

• Pre-decrement yields an lvalue that refers to the operand: std::addressof(--a) == std::addressof(a);
• Post-decrement yields the previous value of the operand: if bool(a == b), then bool(a-- == b).
• Post-decrement and pre-decrement perform the same modification on its operand: If bool(a == b), then after evaluating both a-- and --b, bool(a == b) still holds.
• Increment and decrement are inverses of each other:

• If a is incrementable and bool(a == b), then bool(--(++a) == b).
• If bool(a == b), then bool(++(--a) == b).

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.