Re: Combinatorica versus new graphs in V8

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• Subject: [mg132477] Re: Combinatorica versus new graphs in V8
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Thu, 27 Mar 2014 04:59:34 -0400 (EDT)
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```I believe there's NO way to implement multiple edges in a
System`Graph object. In fact, you undoubtedly saw, when you tried, the error message:

Graph::supp: Mixed graphs and multigraphs are not supported.

Moving the functionality of the graph-theoretic functions from the Combinatorica add-on to the kernel has been a slow process over several versions of Mathematica and evidently is not yet complete.

We can only hope that the next version of Mathematica, already documented in preliminary form at

http://reference.wolfram.com/language/

will allow multiple edges at long last.

On Mar 26, 2014, at 3:23 AM, E. Martin-Serrano <eMartinSerrano at telefonica.net> wrote:

> Hi,
>
> I am unable to see how to  implement multi edge graphs for pairs of vertices
> in V8.
>
> With the =91Combinatorica=92 package this was easy to do as in
>
> << Combinatorica`
>
> g = Combinatorica`Graph[{{{1, 2}}, {{2, 3}}, {{2, 3}}, {{2, 3}} , {{2, 3}}},
> {{{0, 0}}, {{1, 1}}, {{2, 0}}}]
>
> ShowGraph[g]
>
> Here I have three =91{2,3}=92 concurrent edges for the  vertices pair {2,3}
>
> The following should be equivalent for the V8  kernel implementation of
> graphs
>
> System`Graph[{UndirectedEdge[1,2], UndirectedEdge[2,3], UndirectedEdge[2,3],
> UndirectedEdge[2,3], UndirectedEdge[2,3]},
>
> VertexCoordinates -> {{0, 0}, {1, 1}, {2, 0}}]
>
> But the multiple edges feature does not work in the way it did in
> =91Combinatorica=92 (It does not work in any way).
>
> Please, could anyone say what I am missing here?
>
>
> E. Martin
>
>
>
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Murray Eisenberg                                murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 240 246-7240 (H)
University of Massachusetts
710 North Pleasant Street
Amherst, MA 01003-9305

```

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