#14126: Count Number of Linear Extensions of a Poset
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Reporter: csar | Owner: sage-combinat
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.8
Component: combinatorics | Resolution:
Keywords: days45 | Work issues:
Report Upstream: N/A | Reviewers:
Authors: aschilling, nthiery, hivert | Merged in:
Dependencies: | Stopgaps:
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Comment (by csar):
Replying to [comment:6 ncohen]:
> `O_o`
>
> Well, shouldn't the two codes that compute the number of linear
extensions be at the same place ?... A choice could be madebetween the two
with an argument to `cardinality()`.
>
> Nathann
Fair point. `cardinality()` doesn't seem to live in
`sage.combinat.posets.linear_extensions`, though. It looks like it comes
from the `FiniteEnumeratedSets` category. Is it legitimate to give
`LinearExtensionsOfPoset` a cardinality function with an argument to
choose between the `_cardinality_from_iterator` from
`FiniteEnumeratedSets` and counting recursively? My understanding of how
categories are meant to work does not extend this far.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14126#comment:9>
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