#14003: Implementation of a rank symmetric test for posets
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Reporter: stumpc5 | Owner: sage-combinat
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.4
Component: combinatorics | Resolution:
Keywords: posets | Merged in:
Authors: Christian Stump | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by stumpc5):
Currently, it is only implemented for ranked posets. This is, for posets
admitting a rank function that is 0 on minimal elements and an upwards
cover relations increases the rank by 1.
More generally, one can define more generally the rank of an element in a
poset to be the distance (in the graph sense of the Hasse diagram) to a
minimal element. For this, every element should be supposed to have finite
distance. In ranked posets, this is equivalent to the above definition.
Either way, your disjoint union of two chains of different lengths is
therefore not rank-symmetric (the rank sizes are 2,2,...,2,1,...,1 with
the number of 2's being the minimal of the two lengths, and the number of
1's being max-min.
I'd (obviously) be happy if you would take over this ticket!
Thanks, Christian
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Ticket URL: <http://trac.sagemath.org/ticket/14003#comment:7>
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