Boost C++ Libraries

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Bidirectional Iterator

Description

A Bidirectional Iterator traverses a Sequence allowing movement in either direction one element at a time.

Notation

i: A Bidirectional Iterator
I: A Bidirectional Iterator type
M: An MPL integral constant
N: An integral constant

Refinement of

Forward Iterator

Expression requirements

In addition to the requirements defined in Forward Iterator, the following expressions must be valid:

Expression	Return type	Runtime Complexity
`next(i)`	Bidirectional Iterator	Constant
`prior(i)`	Bidirectional Iterator	Constant
`advance_c<N>(i)`	Bidirectional Iterator	Constant
`advance<M>(i)`	Bidirectional Iterator	Constant

Meta Expressions

Expression	Compile Time Complexity
`result_of::prior<I>::type`	Amortized constant time

Expression Semantics

The semantics of an expression are defined only where they differ from, or are not defined in Forward Iterator

Expression	Semantics
`prior(i)`	An iterator to the element preceding `i`

Invariants

In addition to the invariants of Forward Iterator, the following invariants always hold:

prior(next(i)) == i && prior(next(i)) == next(prior(i))
prior(i) == advance_c<-1>(i)
Using prior to traverse a sequence will never return a previously seen position

Models

std::pair iterator
boost::array iterator
vector iterator
map iterator
single_view iterator
iterator_range (where adapted sequence is a Bidirectional Sequence)
transform_view (where adapted sequence is a Bidirectional Sequence)
reverse_view