#14403: Symbolic charpoly broken
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Reporter: nbruin | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-5.11
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Dependencies:
Stopgaps: |
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Comment (by nbruin):
Replying to [comment:14 gagern]:
> I don't know sage development structures and politics. Is this a
personal opinion, or does this come with enough authority to indicate this
as the direction to go?
As far as I'm concerned it's common sense. I won't claim authority for my
own opinion concerning sage, though.
> > {{{
> > sage: P.<x>=QQ[]
> > sage: M=matrix(2,2,[x,1,1,x])
> > sage: M.charpoly()
> > x^2 - 2*x*x + x^2 - 1
> > }}}
>
> Personally, I'd consider this a bug.
I agree it's nasty, but it's there. The problem is that you can have
arbitrarily nastily nested structures: `QQ['s']['x']['u']['y']`. People
could even name their number field generators or finite field generators
`x`.
> How many rings are there? How many of them have elements which you can
name? While I agree that this might require considerable effort, I do have
hope and would consider such an endeavour worthwhile.
It has to be low-cost, though. You're competing with choosing `x` just
blindly.
> One thing which I ''can'' do is this: adapt my patch to do ''only'' the
fix you quoted plus a few doctests. Then I would file another ticket for
the fixes to the `expression.polynomial` even though `charpoly` no longer
needs them,
You might as well fix polynomial.
> and yet another one for the broader question of choosing a suitable
variable name for `charpoly` (and similar situations if you can think of
some).
Yes, because I think it's not clear yet how to solve this properly and
it's something that is a wider problem than just SR.
--
Ticket URL: <http://trac.sagemath.org/ticket/14403#comment:15>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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