#19191: LatticePoset: add is_planar()
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.9
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: Jori Mäntysalo | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/latticeposet__add_is_planar__|
c669ecbf2476518175f0719ba25e76cdc05f1521
Dependencies: | Stopgaps:
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Comment (by jmantysalo):
"A partially ordered set (poset) is planar if it has a planar Hasse
diagram."? Quite short...
How about
"A lattice is planar if it has a planar Hasse diagram --- that is, it can
be drawn to a plane without crossing lines and every covering relationg
directed upwards."?
And yes, this function could be defined on a general poset. But then it is
NP-complete.
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Ticket URL: <http://trac.sagemath.org/ticket/19191#comment:10>
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