#16553: Clean IncidenceStructure
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Reporter: vdelecroix | 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:
Vincent Delecroix | Commit:
Report Upstream: N/A | b8012e72038dffa51cc60b0af19283881dec2860
Branch: public/16553v2 | Stopgaps:
Dependencies: |
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Comment (by vdelecroix):
Replying to [comment:80 ncohen]:
> Yo !
>
> > Yes, because of the reordering of the columns.
>
> Ok !
>
> > And the implementation is stupid, if the blocks are sorted, one would
do
> Yep.
>
> > And... Haaaa.... it is very bad to reorder the blocks:
> > Taking dual should just be matrix transposition!! One question: what
do you think of '''not''' reordering the blocks? (which is a different
from the question "sorting each block")
>
> You should stop letting this function decide of how we should implement
everything else. An incidence structure is isomorphic to its double dual
and that's cool. We have more things to care about than making the vertex
set equal to the set of blocks when we take the dual : anyway we cannot do
that without losing the ability to iterate on the elements of a block.
>
> Accept that.
No. It is more than isomorphic. There is a canonical isomorphism (that is
lost because of the reordering)! But, for the sake of that ticket let say
that I do accept that.
--
Ticket URL: <http://trac.sagemath.org/ticket/16553#comment:81>
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