Version 5.0 The LEDA User Manual

used only as a “Trojan horse,” which carries the pointer to the counter without affecting
the code of the algorithm.
template
bool break_condition (const Iter&) { ... }
template
void dummy_algorithm(ONodeIt& it, OAdjIt& it2) {
while (it.valid()) {
for (it2.update(it); it2.valid() && !break_condition(it2); ++it2)
++it;
}
}
int write_count(graph& G) {
typedef DummyObserver
typedef SimpleCountObserver
typedef ObserverNodeIt
typedef ObserverAdjIt
DummyObs;
CountObs;
ONodeIt;
OAdjIt;
}
DummyObs observer;
ONodeIt it(observer,NodeIt(G));
CountObs observer2(observer);
OAdjIt it2(observer2,AdjIt(G));
dummy_algorithm(it,it2);
return it2.get_observer().counter();
13.12 STL Iterator Wrapper ( STLNodeIt )
1. Definition
An instance it of class STLNodeIt< DataAccessor, Iter > is a STL iterator wrapper for
node iterators (e.g. NodeIt, FilterNodeIt). It adds all type tags and
methods that are necessary for STL conformance; see the standard draft working paper
for details. The type tag value type is equal to typename DataAccessor::value type
and the return value of operator*.
Class STLEdgeIt and STLAdjIt 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. DataAccessor
must be a data accessor.