Version 5.0 The LEDA User Manual

13.9 Filter Node Iterator ( FilterNodeIt )
1. Definition
An instance it of class FilterNodeIt< Predicate, Iter > encapsulates an object of type Iter
and creates a restricted view on the set of nodes over which this internal iterator iterates.
More specifically, all nodes that do not fulfill the predicate defined by Predicate are
filtered out during this traversal.
Class FilterEdgeIt and FilterAdjIt are defined analogously, i.e. can be used for edge
iterators or adjacency iterators, respectively.
Precondition: The template parameter Iter must be a node iterator, e.g. NodeIt or
FilterNodeIt. Predicate must be a class which provides a method
operator( ) according to the following signature: bool operator() (Iter).
#include < LEDA/graph/graph iterator.h >
2. Creation
FilterNodeIt< Predicate, Iter > it;
introduces a variable it of this class, not bound to a predicate or
iterator.
FilterNodeIt< Predicate, Iter > it(const Predicate& pred, const Iter& base it);
3. Operations
introduces a variable it of this class bound to pred and base it.
void
it.init(const Predicate& pred, const Iter& base it)
initializes it, which is bound to pred and base it afterwards.
Precondition: it is not yet bound to a predicate or
iterator.
4. Implementation
Constant overhead.
5. Example
Suppose each node has an own colour and we only want to see those with a specific colour,
for example red (we use the LEDA colours). At first the data structures:
GRAPH G;
NodeIt it(G);