#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 vdelecroix):
Replying to [comment:5 vdelecroix]:
> Replying to [comment:4 ncohen]:
> > > This is confusing.
> >
> > What is confusing ? That blocks are sets of points ? `O_o`
>
> No, that points are blocks of the dual!
>
> > > Basically, we do not care too much about the data type of the blocks
as soon as `__len__`, `__iter__` and `__contains__` are correctly
implemented, right... But it does not work with dual.
> >
> > Why doesn't it work with duals ?
>
> Because the blocks of the duals are the point. And the dual of the dual
is (canonically isomorphic) to the initial design.
>
> > > One option is to do like posets where the ordering is implemented in
the poset itself and not in the elements. We would implement the incidence
structure at the level of `IncidenceStructure` and not at the level of
points/blocks. In other words we would forbid `p in block`.
> >
> > ............
> >
> > Yeah, let's make it impossible to iterate on blocks. That will be
better.
All right: what about intersection? do we want `b1.intersection(b2)`
available?
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Ticket URL: <http://trac.sagemath.org/ticket/16553#comment:7>
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