#19191: LatticePoset: add is_planar()
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_info
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__|
da6a1f9536ac362eef45f565515c752afdf9c84f
Dependencies: #19193 | Stopgaps:
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Comment (by ncohen):
Okay. You are right. This guy cites the same definition that you cite:
http://mathoverflow.net/questions/198116/is-a-distributive-lattice-planar-
iff-it-admits-no-b3-sublattice
And, more importantly, this book [1] on page 93 (bottom). Or this
dissertation [2] page 23.
So you were right from the beginning. And I still can't believe how on
earth they thought wise to have two such definitions coexist when they are
so close to each other. We end up with results like "there are posets
whose hasse diagram is not planar, though the hasse diagram (as a graph)
is planar".
Okay. So what do we do:
I obviously prefer it to be named "is_upward_planar", but that just says
that I would prefer the standard poset terminology to be "is upward
planar". Truth it that people working on posets expect it to be written
"is_planar", so that's probably how it should be named.
Sorry for the loss of time. I guess I just needed some recent publications
which did what your 72 paper does, i.e. say explicitly that planarity is
not graph planarity.
I will now take your branch and work a bit on the documentation, just to
make sure that people like me would not make the mistake if they read it.
If they just read the function's name, well, they are lost.
Nathann
[1] http://www.springer.com/us/book/9783319064123
[2] https://tu-
dresden.de/Members/christian.zschalig/dateien/dissertation_zschalig
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Ticket URL: <http://trac.sagemath.org/ticket/19191#comment:25>
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