Re: [jgrapht-users] getEdgeWeight in weighted Graph

[Joris K. <de...@gm...>]

Hi John,

Thanks for your effort! A NullPointerException if perfectly fine and indeed
a better choice than the UnsupportedArgumentException.

br,

Joris


On Fri, Mar 21, 2014 at 6:14 PM, John Sichi <js...@gm...> wrote:

> I'll make the change (but I think for consistency with existing code,
> I'll use NullPointerException instead of
> UnsupportedArgumentException).
>
> On Fri, Mar 21, 2014 at 1:02 PM, Alex Moir
> <am...@di...> wrote:
> > Good catch, I agree.
> >
> >
> >
> > From: Javier MV [mailto:jav...@dc...]
> > Sent: Friday, March 21, 2014 12:56 PM
> > To: jgr...@li...
> > Subject: Re: [jgrapht-users] getEdgeWeight in weighted Graph
> >
> >
> >
> > +1
> >
> >
> >
> > On Fri, Mar 21, 2014 at 4:01 PM, Georg Hieronimus
> > <geo...@go...> wrote:
> >
> > i strongly agree with your suggestion.
> >
> >  i already had the problem by myself, but forgot to write a pull request
> > afterwards ....
> >
> > It's quiet horrible to find bugs, if you dont know about the current
> > behavior.
> >
> >
> >
> > On 21 March 2014 19:56, Joris Kinable <de...@gm...> wrote:
> >
> > Dear,
> >
> >
> >
> > In the latest version of jgrapht (and perhaps also in other versions),
> the
> > getEdgeWeight(E e) function is implemented as follows:
> >
> >
> >
> > public double getEdgeWeight(E e)
> >
> >     {
> >
> >         if (e instanceof DefaultWeightedEdge) {
> >
> >             return ((DefaultWeightedEdge) e).getWeight();
> >
> >         } else {
> >
> >             return WeightedGraph.DEFAULT_EDGE_WEIGHT;
> >
> >         }
> >
> >     }
> >
> >
> >
> >
> >
> > If e==null, i.e. the edge does not exist, then this function will return
> > DEFAULT_EDGE_WEIGHT. This is strange as often invoking the getEdgeWeight
> > function on a non-existing edge is simply a bug.
> >
> >
> >
> > I would suggest to modify the above function to something like:
> >
> > public double getEdgeWeight(E e)
> >
> >     {
> >
> >         if (e instanceof DefaultWeightedEdge) {
> >
> >             return ((DefaultWeightedEdge) e).getWeight();
> >
> >         } else if(e==null){
> >
> >            throw new UnsupportedArgumentException("Edge cannot be null");
> >
> >         }else{
> >
> >             return WeightedGraph.DEFAULT_EDGE_WEIGHT;
> >
> >         }
> >
> >     }
> >
> >
> >
> > One common error would be something like:
> >
> > Edge e=graph.getEdge(i,j); //Edge (i,j) is not part of the graph, so
> > e==null;
> >
> > cost += graph.getEdgeWeight(e); //Correct, does not invoke an exception
> >
> >
> >
> >
> >
> > At the very least, the javadoc for the getEdgeWeight function should
> mention
> > the above pitfall by specify that invoking the getEdgeWeight function on
> > null returns WeightedGraph.DEFAULT_EDGE_WEIGHT so it's the user's
> problem to
> > check whether the edge is not equal to null.
> >
> >
> >
> > This is just a suggestion. If there is support for this change, I'll
> make a
> > change request.
> >
> >
> >
> > br,
> >
> >
> >
> > Joris
> >
> >
> >
> >
> ------------------------------------------------------------------------------
> > Learn Graph Databases - Download FREE O'Reilly Book
> > "Graph Databases" is the definitive new guide to graph databases and
> their
> > applications. Written by three acclaimed leaders in the field,
> > this first edition is now available. Download your free book today!
> > http://p.sf.net/sfu/13534_NeoTech
> > _______________________________________________
> > jgrapht-users mailing list
> > jgr...@li...
> > https://lists.sourceforge.net/lists/listinfo/jgrapht-users
> >
> >
> >
> >
> >
> ------------------------------------------------------------------------------
> > Learn Graph Databases - Download FREE O'Reilly Book
> > "Graph Databases" is the definitive new guide to graph databases and
> their
> > applications. Written by three acclaimed leaders in the field,
> > this first edition is now available. Download your free book today!
> > http://p.sf.net/sfu/13534_NeoTech
> > _______________________________________________
> > jgrapht-users mailing list
> > jgr...@li...
> > https://lists.sourceforge.net/lists/listinfo/jgrapht-users
> >
> >
> >
> >
> > --
> > Javier MV
> >
> >
> >
> ------------------------------------------------------------------------------
> > Learn Graph Databases - Download FREE O'Reilly Book
> > "Graph Databases" is the definitive new guide to graph databases and
> their
> > applications. Written by three acclaimed leaders in the field,
> > this first edition is now available. Download your free book today!
> > http://p.sf.net/sfu/13534_NeoTech
> > _______________________________________________
> > jgrapht-users mailing list
> > jgr...@li...
> > https://lists.sourceforge.net/lists/listinfo/jgrapht-users
> >
>
>
> ------------------------------------------------------------------------------
> Learn Graph Databases - Download FREE O'Reilly Book
> "Graph Databases" is the definitive new guide to graph databases and their
> applications. Written by three acclaimed leaders in the field,
> this first edition is now available. Download your free book today!
> http://p.sf.net/sfu/13534_NeoTech
> _______________________________________________
> jgrapht-users mailing list
> jgr...@li...
> https://lists.sourceforge.net/lists/listinfo/jgrapht-users
>