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< h1 class = "title" > Bidirectional Traversal Concept< / h1 >
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< p > A class or built-in type < tt class = "literal" > < span class = "pre" > X< / span > < / tt > models the < em > Bidirectional Traversal< / em >
concept if, in addition to < tt class = "literal" > < span class = "pre" > X< / span > < / tt > meeting the requirements of Forward
Traversal Iterator, the following expressions are valid and respect
the stated semantics.< / p >
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< tr > < th colspan = "3" > Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal
Iterator)< / th >
< / tr >
< tr > < th > Expression< / th >
< th > Return Type< / th >
< th > Assertion/Semantics /
Pre-/Post-condition< / th >
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< tr > < td > < tt class = "literal" > < span class = "pre" > --r< / span > < / tt > < / td >
< td > < tt class = "literal" > < span class = "pre" > X& < / span > < / tt > < / td >
< td > pre: there exists
< tt class = "literal" > < span class = "pre" > s< / span > < / tt > such that < tt class = "literal" > < span class = "pre" > r< / span >
< span class = "pre" > ==< / span > < span class = "pre" > ++s< / span > < / tt > . post:
< tt class = "literal" > < span class = "pre" > s< / span > < / tt > is
dereferenceable.
< tt class = "literal" > < span class = "pre" > --(++r)< / span > < span class = "pre" > ==< / span > < span class = "pre" > r< / span > < / tt > .
< tt class = "literal" > < span class = "pre" > --r< / span > < span class = "pre" > ==< / span > < span class = "pre" > --s< / span > < / tt >
implies < tt class = "literal" > < span class = "pre" > r< / span > < span class = "pre" > ==< / span >
< span class = "pre" > s< / span > < / tt > . < tt class = "literal" > < span class = "pre" > & r< / span > < span class = "pre" > ==< / span > < span class = "pre" > & --r< / span > < / tt > .< / td >
< / tr >
< tr > < td > < tt class = "literal" > < span class = "pre" > r--< / span > < / tt > < / td >
< td > convertible to < tt class = "literal" > < span class = "pre" > const< / span > < span class = "pre" > X& < / span > < / tt > < / td >
< td > < pre class = "first last literal-block" >
{
X tmp = r;
--r;
return tmp;
}
< / pre >
< / td >
< / tr >
< tr > < td > < tt class = "literal" > < span class = "pre" > iterator_traversal< X> ::type< / span > < / tt > < / td >
< td > Convertible to
< tt class = "literal" > < span class = "pre" > bidirectional_traversal_tag< / span > < / tt > < / td >
< td > < / td >
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< a class = "reference" href = "BidirectionalTraversal.rst" > View document source< / a > .
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