Re: [jgrapht-users] getEdgeWeight in weighted Graph

[Javier MV <jav...@dc...>]

+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
>>
>>
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>>
>
>
> ------------------------------------------------------------------------------
> 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