Boost C++ Libraries

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Bidirectional Sequence

Description

A Bidirectional Sequence is a Forward Sequence whose iterators model Bidirectional Iterator.

Refinement of

Forward Sequence

Notation

s: A Bidirectional Sequence
S: A Bidirectional Sequence type
o: An arbitrary object
e: A Sequence element

Valid Expressions

In addition to the requirements defined in Forward Sequence, for any Bidirectional Sequence the following must be met:

Expression	Return type	Type Requirements	Runtime Complexity
`begin(s)`	Bidirectional Iterator		Constant
`end(s)`	Bidirectional Iterator		Constant
`back(s)`	Any type		Constant
`back(s) = o`	Any type	`s` is mutable and `e = o`, where `e` is the first element in the sequence, is a valid expression.	Constant

Result Type Expressions

Expression	Compile Time Complexity
`result_of::begin<S>::type`	Amortized constant time
`result_of::end<S>::type`	Amortized constant time
`result_of::back<S>::type`	Amortized constant time

Expression Semantics

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

Expression	Semantics
`back(s)`	The last element in the sequence; see `back`.

Models

std::pair
boost::array
vector
map
reverse_view
single_view
iterator_range (where adapted sequence is a Bidirectional Sequence)
transform_view (where adapted sequence is a Bidirectional Sequence)
zip_view (where adapted sequences are models of Bidirectional Sequence)