#4656: [with patch, needs work] power series with zero p-adic coefficients
---------------------------+------------------------------------------------
Reporter: wuthrich | Owner: was
Type: defect | Status: new
Priority: minor | Milestone: sage-4.0
Component: number theory | Keywords: padic powerseries
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Comment(by wuthrich):
I looked into the problem. It is not due to a bug in supersingular, but
due to the following strange behaviour. This happens to me with the above
second patch.
I don't think that is ok :
{{{
sage: R = Qp(5,10)
sage: RT.<T> = R[[]]
sage: f = O(5^3) + O(5)*T +O(T^2)
sage: f
O(5^3) + O(5)*T + O(T^2)
sage: f[1]
0
}}}
f is now printed correctly, but the coefficient is not. In fact the
precision of the coefficient is lost (and that happens without the patch,
too):
{{{
sage: a= f[1]
sage: a
0
sage: a.precision_absolute()
+Infinity
}}}
Now, this looks really bad:
{{{
sage: v = matrix([[1,0],[0,1]])*vector([1,f])
sage: v
(1 + O(5^10), )
sage: v[1]
sage: type(v[1])
<type 'sage.rings.power_series_poly.PowerSeries_poly'>
}}}
I must admit that I do not understand what is going on and if this ticket
is in fact related to other known issues with p-adic series.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4656#comment:6>
Sage <http://sagemath.org/>
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