[Lemon-user] Code snippet to iterate over a map ?

[Diego Taylor]

Hi Péter,

Thank for your prompt response. I tried to follow the "MapIt route" without
success, the compilation gives:

scheduler.cc: In member function ‘void
DAGScheduler::put(lemon::ListDigraphBase::Node)’:
scheduler.cc:48: error: no matching function for call to
‘lemon::MapExtender<lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc>
>::MapIt::MapIt(const
lemon::DigraphExtender<lemon::ListDigraphBase>::NodeMap<lemon::ListDigraphBase::Arc>&)’
/usr/local/include/lemon/bits/map_extender.h:95: note: candidates are:
lemon::MapExtender<_Map>::MapIt::MapIt(const lemon::MapExtender<_Map>&,
const typename _Map::Key&) [with _Map =
lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc>]
/usr/local/include/lemon/bits/map_extender.h:91: note:
lemon::MapExtender<_Map>::MapIt::MapIt(lemon::MapExtender<_Map>&) [with _Map
= lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc>]
/usr/local/include/lemon/bits/map_extender.h:89: note:
lemon::MapExtender<_Map>::MapIt::MapIt(lemon::Invalid) [with _Map =
lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc>]
/usr/local/include/lemon/bits/map_extender.h:87: note:
lemon::MapExtender<_Map>::MapIt::MapIt() [with _Map =
lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc>]
/usr/local/include/lemon/bits/map_extender.h:80: note:
lemon::MapExtender<lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc>
>::MapIt::MapIt(const
lemon::MapExtender<lemon::DefaultMap<lemon::DigraphExtender<lemon::ListDigraphBase>,
lemon::ListDigraphBase::Node, lemon::ListDigraphBase::Arc> >::MapIt&)
make: *** [dgraph] Error 1

The line is:
---------- o ----------
const Bfs<ListDigraph>::PredMap& predMap = bfs.predMap();
typedef ListDigraph::NodeMap<ListDigraph::Arc> PM;

for(PM::MapIt it(predMap); it != INVALID; ++it) {}
---------- o ----------

Thank you,
Diego

2010/6/24 Kovács Péter <kpeter at inf.elte.hu>

> Hi,
>
> If you would like to iterate over all nodes, then you can simply use
> NodeIt:
>
>  for (GraphType::NodeIt u(g); u != INVALID; ++u)
>    cout << g.id(u) << " pred arc: " << g.id(bfs.predArc(u)) << "\n";
>
>  for (GraphType::NodeIt u(g); u != INVALID; ++u)
>    cout << g.id(u) << " pred node: " << g.id(bfs.predNode(u)) << "\n";
>
> If your PredMap is a standard NodeMap<Arc>, then you can also use its MapIt
> or ConstMapIt iterator type (though it is not documented yet as far as I
> know):
>
>  typedef GraphType::NodeMap<GraphType::Arc> PredMap;
>  PredMap pred = bfs.predMap();
>  for (PredMap::MapIt it(pred); it != INVALID; ++it)
>    cout << g.id(it) << " pred arc: " << g.id(*it) << "\n";
>
> On the other hand, if you would like to iterate over the visited nodes only
> (for efficiency reasons), then you could either
>  1. run the algorithm step-by-step and do the required operations meantime
> (consider to use init(), addSource(), emptyQueue(), nextNode(),
> processNextNode() functions) or
>  2. run the algorithm at once using run(), but use a special ProcessedMap
> to keep track the visited nodes (consider to use e.g. LoggerBoolMap for this
> purpose):
>
> http://lemon.cs.elte.hu/pub/doc/1.2/a00515.html#g21ca379ec2c92eccd71b76df0a9eee8c
> Once you stored the nodes in a container, you can easily iterate over them
> and you can obtain pred values using predNode(), predArc() or predMap().
>
> I hope that I could answer your questions.
>
> Best regards,
> Peter
>
>
>
>  Hi,
>>
>> I can't get the map iterator from predMap to work after a bfs (don't
>> know the syntaxis for that). How can I iterate over all results
>> including nodes (keys) and values? I couldn't find an example either. A
>> small code snippet will be more than helpful.
>>
>>
>> Thank You,
>> Diego
>>
>
>
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