On Sat, Mar 05, 2011 at 09:36:45PM -0800, Andrey Novoseltsev wrote:
> I have discovered that a fan consisting only of the origin cannot
> compute its cone lattice due to the following behaviour:
>
> sage: G = DiGraph(1)
> sage: print G
> Digraph on 1 vertex
> sage: P = Poset(G)
> sage: print P
> Finite poset containing 1 elements
> sage: print P.bottom()
> 0
> sage: print P.top()
> None
>
> Is it a bug? It seems to me that 0 in this case is both top and bottom
> and the minimal and the maximal element.
Definitely a bug, due to an incorrect test in FinitePoset.top:
if hasse_top:
It should be:
if hasse_top is not None:
This was discussed recently, and there is a ticket for it, or for
something very similar (sorry, I don't have a connection right now to
check which one).
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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