Dear Kazek,
This is actually the correct behavior due to incorrect input. You should
pass in a list of vertices, not a list of faces to remove (the name of the
method only says it will remove 1 face, not multiple). Now returning a
non-None object is sort of the indicator that nothing is done (by looking
at the source code), but I'm not convinced of having the different return
types. Instead, what I believe you want is this:
sage: Z = SimplicialComplex([[0,1,2,3]]);Z
Simplicial complex with vertex set (0, 1, 2, 3) and facets {(0, 1, 2, 3)}
sage: Z.remove_face([0,1])
sage: Z.faces()
{-1: {()},
0: {(0,), (1,), (2,), (3,)},
1: {(0, 2), (0, 3), (1, 2), (1, 3), (2, 3)},
2: {(0, 2, 3), (1, 2, 3)}}
Although there probably should be a remove_faces() method too...
Best,
Travis
On Saturday, February 10, 2018 at 3:16:43 PM UTC-6, Kazimierz Kurz wrote:
>
> The following code gives incorrect result.
>
> I create simplicial complex Z.
>
> Z = SimplicialComplex([[0,1,2,3]]);Z
>
> Simplicial complex with vertex set (0, 1, 2, 3) and facets {(0, 1, 2, 3)}
>
>
> It has correct faces:
>
> Z.faces()
>
> {0: set([(3,), (0,), (1,), (2,)]), 1: set([(2, 3), (0, 2), (1, 3), (1, 2),
> (0, 3), (0, 1)]), 2: set([(0, 2, 3), (0, 1, 2), (1, 2, 3), (0, 1, 3)]), 3:
> set([(0, 1, 2, 3)]), -1: set([()])}
>
>
> X1=Z.remove_face([(0,1)]);X1
>
> Simplicial complex with vertex set (0, 1, 2, 3) and facets {(0, 1, 2, 3)}
>
>
> X1.faces()
>
> {0: set([(3,), (0,), (1,), (2,)]), 1: set([(2, 3), (0, 2), (1, 3), (1, 2),
> (0, 3), (0, 1)]), 2: set([(0, 2, 3), (0, 1, 2), (1, 2, 3), (0, 1, 3)]), 3:
> set([(0, 1, 2, 3)]), -1: set([()])}
>
> After face removal it is still there.
> It was very old bug in Sage 5.6
> My code doesn work correctly both in my Sage 6.8 and in Cocalc Internet
> platform:
>
> https://cocalc.com/share/52e64765-ec22-4637-9821-6528d33ab85e/2018-02-10-220535.sagews?viewer=share
>
>
> Best Regards
> Kazek Kurz
>
>
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