C++ concepts: BidirectionalIterator

 

C++

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Technical Specifications

 

C++ concepts

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DefaultConstructible CopyAssignable CopyConstructible	MoveAssignable (C++11) MoveConstructible (C++11) Destructible
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Iterator OutputIterator InputIterator	ForwardIterator BidirectionalIterator RandomAccessIterator ContiguousIterator (C++17)
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FormattedInputFunction UnformattedInputFunction	FormattedOutputFunction UnformattedOutputFunction
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A BidirectionalIterator is a ForwardIterator that can be moved in both directions (i.e. incremented and decremented).

Requirements

The type It satisfies BidirectionalIterator if

• The type It satisfies ForwardIterator

And, given

• a and b, iterators of type It
• reference, the type denoted by std::iterator_traits<It>::reference

The following expressions must be valid and have their specified effects

Expression	Return	Equivalent expression	Notes
--a	It&		Preconditions: a is decrementable (there exists such b that a == ++b) Postconditions: a is dereferenceable --(++a) == a If --a == --b then a == b &a == &--a
a--	convertible to const It&	It temp = a; --a; return temp;
*a--	reference

A mutable BidirectionalIterator is a BidirectionalIterator that additionally satisfies the OutputIterator requirements.

Notes

The begin iterator is not decrementable and the behavior is undefined if --container.begin() is evaluated.

A bidirectional iterator does not have to be dereferenceable to be decrementable (in particular, the end iterator is not dereferenceable but is decrementable)

See also

• Iterator library