On Tue, Mar 22, 2011 at 07:09:09AM -0700, Anne Schilling wrote:
> Impressive, your work on posets!
:-)
Kudos also go to Christian and Frédéric!
Oh, and I should mention that if the facade option was so far
straightforward to implement, that's because Franco's original code
was well written and encapsulated.
> >- Currently P.hasse_diagram() returns a graph G whose nodes are the
> > elements of P (wrapped as elements of P; so one needs to do
> > x.element to actually get the original element). This graph is still
> > in the HasseDiagram class. The issue is that HasseDiagram's expect
> > their vertices to be 0,1,...,n-1, so most of the extra methods just
> > break.
> >
> > Option 1: P.hasse_diagram() returns a plain digraph
> >
> > Option 2: P.hasse_diagram() returns the internal HasseDiagram, with
> > vertices labelled 0,1,...,n
> >
> > What do you prefer? I personally vote for 2; as a user, that's what
> > I would expect.
> I would probably prefer 2 as well.
Arr, sorry, I actually meant 1. For my penance a concrete example to
think about::
sage: P = Poset((Subsets(2), attrcall("issubset")))
Option (1):
sage: P.hasse_diagram().edges()
[({}, {2}, None), ({}, {1}, None), ({2}, {1, 2}, None), ({1}, {1, 2},
None)]
sage: P.hasse_diagram().__class__
<class 'sage.graphs.digraph.DiGraph'>
Option (2):
sage: P.hasse_diagram().edges()
[(0, 1, None), (0, 2, None), (1, 3, None), (2, 3, None)]
sage: P.hasse_diagram().__class__
<class 'sage.combinat.posets.hasse_diagram.HasseDiagram'>
> > Another question is whether we want the vertices P.hasse_diagram()
> > to be wrapped or not. And if we are unhappy with the situation, is
> > still time to change this?
>
> If it is possible not to wrap them, I think this would be good.
> At least I ran into some problems when playing with posets in the past.
Yup. Please try out the facade option. I'd love to have feedback on it!
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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