On Sun, Aug 23, 2009 at 11:59 PM, John H Palmieri<jhpalmier...@gmail.com> wrote:
>
> On Aug 10, 8:41 pm, Rafael Villarroel <rvf0...@gmail.com> wrote:
> Some comments: first, in general, these functions would be better as
> "methods", so that they would be called as
>
> S.is_free_face(s)
> S.free_face_removed()
> S.collapsed_complex()
>
> That is, they would be included in simplicial_complex.py, like
> "remove_face", etc.
>
>> # a free face is one that is contained properly in exactly one maximal face
>> def is_free_face (S,s):
>
> To turn into a method, change the previous line to "def is_free_face
> (self, s):", and in general replace "S" with "self".
>
>> def f(x): return set(s)<=set(x)
>> return not (Simplex(s) in S.facets()) and len(filter(f,S.facets()))==1
>>
Thanks for your answer!
I have added
def is_free_face (self,s):
"""
A free face is one that is contained properly in exactly one
maximal face.
Removing a free face from a complex does not change the
homotopy type of the complex.
"""
def f(x): return set(s)<=set(x)
return not (Simplex(s) in self.facets()) and
len(filter(f,self.facets()))==1
to the end of
~/sage-4.0/devel/sage-main/build/sage/homology/simplicial_complex.py
(since it was the only one of the four simplicial_complex.py that I
have under ~/sage-4.0 that
seemed to make a difference). But now I get
sage: S.is_free_face(l[1])
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/rafael/.sage/temp/rafael_desktop/1477/_home_rafael_sage_simplicial_sage_0.py
in <module>()
TypeError: 'set' object does not support indexing
So, is there something else I have to do to make "is_free_face" work
as a method?
As soon as I get this working, I think I could work through your other
suggestions.
I think that it depends of the complex which method would be faster.
For example, with
a (complete) simplex, any vertex is a free face, and collapsing this
simplex completely
only takes as many steps as there are vertices.
Best regards,
Rafael
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