#2462: Odd results when adding Laurent series
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Reporter: ljpk | Owner: tbd
Type: defect | Status: new
Priority: major | Milestone: sage-3.2.1
Component: algebra | Resolution:
Keywords: |
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Changes (by robertwb):
* owner: robertwb => tbd
* component: coercion => algebra
Comment:
I really don't think this is due to coercion, as no coercion is going on
here (all parents are identical, arithmetic is dispatched immediately).
David Harvey is right, in polynomial_element.pyx:3672 we have
{{{
if p is None:
for k from 0 <= k <= self.degree():
if self[k]:
return ZZ(k)
}}}
because self is not detected to be zero earlier (even though it really is)
the loop exits without returning, hence the [boom]. The error, however,
occurred earlier. Somewhere, something's not getting normalized like it
should be. I think the error is in polynomials.
Continuing on David's session,
{{{
sage: f = h.polynomial() - k.polynomial()
sage: f
0
sage: sage: len(f.coeffs())
500
sage: k.degree()
499
sage: k[499] # ?!!
0
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/2462#comment:4>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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