#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):
> For GDD you have an extra assumption of the existence of a lambda:
> {{{
> blocks = [[0,1],[0,2]]
> groups = [[0],[1,2]]
> }}}
> is not a GDD (0 is covered by two blocks, but 1 and 2 are covered by one
block). But "not being in a block" for pairs is an equivalence relation...
Since when do you need to be regular to be a GDD ? Even PBD are not
necessarily regular ! Lambda is about pairs of vertices.
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/16598#comment:18>
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