#18972: twographs and Seidel switching
-------------------------------------+-------------------------------------
Reporter: dimpase | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.9
Component: graph theory | Resolution:
Keywords: | Merged in:
Authors: | Reviewers: Nathann Cohen
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/dimpase/seidelsw | 6bc5cbd678d6d9db6e99ff23489e0e1a720e8569
Dependencies: #18960, #18948, | Stopgaps:
#18988, #18991, #18986, #19018, |
#19019 |
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Comment (by dimpase):
Replying to [comment:83 ncohen]:
> > no, for two-graphs it's the way it is. Should I rename this
`.complement()` as
> > `twograph_complement()`?
>
> HMmmmmm `:-/`
>
> It is true that the "right" notion of "complement" really depends on
what you do when it comes to hypergraphs. I made the other one the default
because it applies to all hypergraphs, and not only to uniform ones.
>
> I thought for a while of your proposition to make it a `new method`, but
then why don't you just use `.complement(uniform=True)`? If you are ready
to leave `.complement` as it is and to create a new function, then do you
really need that function?
Well, the rationale behind the current code is that someone who wants to
take the complement of a two-graph should just call `.complement()` rather
than something more complicated. And indeed, the complement of a two-graph
has a well-established meaning. It's more an implementation artefact that
the base class already has `complement()` defined, and it's not quite the
same. The user should not care about this IMHO.
Same was with `is_regular()`, but you didn't like this as it clashed with
the default, and I made it `is_regular_twograph()`.
It looks rather incoherent now; I'd personally prefer to revert to my old
`is_regular()`, and keep the current `complement()`.
>
> > well, I don't like inplace things. I don't even have an inplace option
for this function.
> > I hope it's OK.
>
> It's surprising, at least for me. Would you object if I added a commit
that makes it an inplace function, with an optional `inplace=False` to get
a copy?
no problem, go ahead with this.
>
> > I'm going to fix the rest and add a construction of two-graphs (more
precisely, certain Seidel adj.matrices, from which the two-graph can be
constructed, if needed) from doubly-transitive permutation groups, i.e.
Taylor two-graphs.
>
> Nice. Could you please do that in another ticket, please? This one is
already dozens of commits long.
OK, on another ticket then, no problem.
--
Ticket URL: <http://trac.sagemath.org/ticket/18972#comment:84>
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