#15698: univariate polynomial ring fraction expansion to power series
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Reporter: rws | Owner: rws
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.1
Component: algebra | Resolution:
Keywords: series expansion fraction ogf | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by pbruin):
The "canonical" syntax for this kind of conversion would be
{{{
sage: S = QQ[['t']] # construct power series ring
sage: S(A) # convert A into it, using default precision
sage: S(A, prec=6) # or using specified precision
}}}
However, the last two lines currently fail with
{{{
TypeError: denominator must be a unit
}}}
The following does work:
{{{
sage: L=S.laurent_series_ring()
sage: L(A)
1 + t + t^2 + t^3 + t^4 + t^5 + t^6 + t^7 + t^8 + t^9 + t^10 + t^11 + t^12
+ t^13 + t^14 + t^15 + t^16 + t^17 + t^18 + t^19 + O(t^20)
}}}
Unfortunately, this does not currently accept a precision argument.
I think the easiest solution for `S(A)` is to fix
`PowerSeriesRing._element_constructor_()` to accept rational functions.
--
Ticket URL: <http://trac.sagemath.org/ticket/15698#comment:2>
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