#16553: Clean IncidenceStructure
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Reporter: vdelecroix | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.3
Component: combinatorial designs | Resolution:
Keywords: | Merged in:
Authors: Nathann Cohen, Vincent | Reviewers:
Delecroix | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Comment (by ncohen):
Yo !
> - I think we also want another bijection `blocks <-> {0, ..., b-1}` to
have well defined incidence matrices. It would also help to choose proper
labels for the dual incidence structure.
Well, the points of the dual incidence structure could be ... Sets ?.. Or
tuples. I mean, the labels of the points of a dual incidence structure
could be the blocks of the original incidence structure.
ANd of course, the blocks would be .. Sets of points from the ground set ?
That's what we want, isn't it ?
> - A better name for `IncidenceStructure` would be `Design`...
Or hypergraph ?... A friend of mine says "geometry" instead of
"hypergraph". Truth it, an incidence structure is a pretty general thing :
http://en.wikipedia.org/wiki/Incidence_structure
> and we also need a class for `GroupDivisibleDesign` and for them we need
an other bijection `groups <-> {0, ..., g-1}`.
Well, we may need to have ".groups()" indeed. We would have GDD at the
bottom, them PBD, BIBD, transversal designs...
The main problem is that orthogonal arrays are not really designs in this
sense.
> - to fit with enumerated set the natural terminology for the bijection
would be `rank/unrank`
> {{{
> class Design:
> def rank_point(self, point): # index of ``point``
> def unrank_point(self, n): # ``n``-th point
> def rank_block(self, block): # index of ``block``
> def unrank_block(self, n): # ``n``-th block
> }}}
Really ? Ewww.. Honestly I'd be glad to avoid things like that and keep
the integer names internal. Users do not need to see that !
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/16553#comment:2>
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