Hi,
> I highly appreciated the last contributions (thanks guys!) but I also
> agree on this point, so let's start from the end.
> I think that, no matter what underlying structure we come up with, the
> user should be able to specify e.g. a weighted edge with something like
>
> public class MyEdge implements Edge, Weighted<Double> { ... }
>
> and be able to immediately use it as an input for all the algorithms,
> without extra steps required. So the average user is happy, while
> "graph geeks" can dig into advanced capabilities and forge their
> personalized weights :)
> I hope we all agree on this as a first step. Complexity comes after.
>
> I'll take my time as well to rethink.
I did think and code a bit more. First of all please take a look at the
updated code: Weighted<W> is an interface (weight W can be any type) and
all the algorithms require edges to implement Weighted<Double> for now
 we did not break it that much ;)
About the "HasPropertyvsProperty" question (as in Comparable vs
Comparator, MonoidElement vs Monoid, etc) I would go for the second one
only. That is, external classes handle all operations on weights.
Downside: the # of method parameters would increase linearly with the
number of properties, but I can live with that (how many properties
would weights have anyway?). On the other hand we have a neat interface
for each property/class (Zero, Semigroup, Monoid, Ordering or
Comparator, etc) and one clean, generic implementation for each
algorithm. Dijkstra's signature becomes something like:
public static <V extends Vertex, W, WE extends WeightedEdge<W>, G
extends DirectedGraph<V, WE>> WeightedPath<V, WE, W> findShortestPath( G
graph, V source, V target, Monoid<W> weightMonoid, Comparator<W>
weightComparator )
Scary uh? But wait, default implementations for Double, Integer, etc.
are way easier. E.g. Dijkstra's shortcut for Double:
public static <V extends Vertex, WE extends WeightedEdge<Double>, G
extends DirectedGraph<V, WE>> WeightedPath<V, WE, Double>
findShortestPath( G graph, V source, V target )
{
return findShortestPath(graph, source, target, new DoubleMonoid(),
new DoubleComparator());
}
where DoubleMonoid and DoubleComparator are part of the library.
If you guys are fine with this, I'm ready to try and patch [graph] with
a Christmas gift :)
Claudio

Claudio Squarcella
PhD student at Roma Tre University
Email address: squarcel@dia.uniroma3.it
Phone: +390657333215
Fax: +390657333612
http://www.dia.uniroma3.it/~squarcel

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