#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 ncohen):
> The abstract of first paper I mentioned starts with "It is shown that a
finite lattice is planar if and only if the (undirected) graph obtained
from its (Hasse) diagram by adding an edge between its least and greatest
elements is a planar graph." And this makes no sense if planarity of
lattices would equal to planarity of graphs.
It *does* make sense. It means that if a lattice is planar, then there is
a drawing of it in which the top and bottom elements appear in the same
face.
> The question is about meaning of Hasse diagram.
As a reviewer, I just want to make sure that what the user will understand
is what actually happens.
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/19191#comment:15>
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