#16598: Useless new classes and a replacement for _check_pbd
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Reporter: ncohen | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.3
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: | Reviewers:
Authors: Nathann Cohen | Work issues:
Report Upstream: N/A | Commit:
Branch: u/ncohen/16598 | fa3c715732a965786f86a2a0ce7087c63294519a
Dependencies: #16553 | Stopgaps:
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Comment (by ncohen):
> Groups are not a parameter.
v and k are not a parameter of a BIBD either, they can be deduced. Same
for K in PBD.
> If you have a GDD, the group are completely determined by the blocks:
define the groups in such way that two points are in the same group if and
only if they do not belong to a common block.
I know, I mentionned it in my last comment....
> So, it makes sense to have `.is_gdd()` at the level of
`IncidenceStructure` and make it returns the groups if needed. We can also
have a method `.groups()` on `IncidenceStructure` without any attribute
`._groups` defined.
>
> What do you think?
I don't like it, you cannot define "groups" properly at this level. What
do you think the "groups" of `IncidenceStructure(3,[[1,2]])` should be ?
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/16598#comment:14>
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