#13566: Simplicial complex examples as singletons
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Reporter: tscrim | Owner: tscrim
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-5.7
Component: algebraic topology | Resolution:
Keywords: simplicial | Work issues:
Report Upstream: N/A | Reviewers: Travis
Scrimshaw
Authors: Christian Nassau, John Palmieri | Merged in:
Dependencies: #13244, #12587 | Stopgaps:
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Comment (by tscrim):
Replying to [comment:25 jhpalmieri]:
> How do you make an immutable simplicial complex mutable? We seem to have
missed adding a `set_mutable` method in #12587, and so now I don't know
how to get a mutable copy of the various examples, short of explicitly
setting the `_is_mutable` attribute.
For example
{{{
sage: S = simplicial_complexes.Sphere(4)
sage: S.is_mutable()
False
sage: T = SimplicialComplex(S, is_mutable=True) # This should work and is
a bug I didn't catch
sage: T.is_mutable()
False
sage: T = SimplicialComplex(S) # This one I'm happy with leaving immutable
sage: T.is_mutable()
False
}}}
However I do think we should also have a method to make a mutable copy, my
suggestions are either `copy()` and/or `make_mutable()`.
> I think this should be fixed very soon, maybe before the other issues in
this ticket.
Agreed. This was something I introduced, so I'll be happy to fix it.
> As far as whether the examples should be immutable, I don't feel
strongly either way. I can see a certain elegance in immutability, but
other examples in Sage don't seem to work like this. I suppose we could
use `UniqueFactory` to create an immutable unique instance, but the
functions (or methods, or whatever) could return a mutable copy each time.
For example:
> {{{
> sage: MatrixSpace(QQ, 3, 3).identity_matrix().is_mutable()
> False
>
> sage: matrix.identity(QQ, 3).is_mutable()
> True
> }}}
> This seems rather odd to me, but I suppose it's an option.
This is very strange to me as well. Part of the thing is the identity
matrix function is cached, so it must return an immutable object.
Best,[[BR]]
Travis
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13566#comment:26>
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