#15948: DynkinDiagram with crossed nodes and labels
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Reporter: vittucek | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.2
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: Vít Tuček | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vittucek/ticket/15948 | bf72707a19157a9728badae4932a8a1f010c6897
Dependencies: | Stopgaps:
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Comment (by vittucek):
Replying to [comment:4 tscrim]:
> I believe it is useful to have the ability to cross out particular nodes
for Dynkin diagrams (I believe the same/similar convention is used for Lie
superalgebras to denote even/odd indices).
>
I'm glad to hear that.
>
> However I think the `node_label` is redundant to the `label` and you are
assuming your indexing set is `1, 2, ..., n`, often which it is not.
Similarly, I'm planning to make Dynkin diagrams more immutable (#15739),
so I'd rather have it return a new `DynkinDiagram` when changing the
crossed out nodes. One last point from a quick look-through, for
comparisons with `None` you should do:
> {{{
> if x is None:
> pass
>
> if x is not None:
> pass
> }}}
>
The labels which are implemented so far are intended for people who
doesn't want to use Bourbaki convention. I think, this feature is not very
well documented. My labels are purely a decoration of nodes, which can be
used i.e. to denote a homogeneous vector bundle over $G/P$. So I guess the
correct thing to do here is to change `node_labels[i]` to
`node_labels[label(i)]`, right?
As for immutability issue, will it be OK, if I just add crossed_nodes and
node_labels to the constructor and get rid of the setters?
>
> I'll check against Kac tonight. Dan and Nicolas might have some more
comments as well.
>
> Best,[[BR]]
> Travis
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Ticket URL: <http://trac.sagemath.org/ticket/15948#comment:7>
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