#11368: can't coerce pari to rational function field
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Reporter: katestange | Owner: robertwb
Type: defect | Status: new
Priority: minor | Milestone: sage-5.13
Component: coercion | Resolution:
Keywords: coercion pari rational | Merged in:
fraction_field string | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Old description:
> The following fails
> {{{
> sage: R.<x,y> = PolynomialRing(QQ)
> sage: S = R.fraction_field()
> sage: S(pari((x+y)/y))
> TypeError: no canonical coercion from Fraction Field of Multivariate
> Polynomial Ring in x, y over Rational Field to Rational Field
> }}}
> However, if you replace (x+y)/y with x+y, it works (in other words,
> polynomials work but rational functions don't).
>
> I think it is probably related that the following fails: (with R and S as
> above)
> {{{
> S('(x+y)/y')
> }}}
> with the same error. Again, polynomial coercion like
> {{{
> S('x+y')
> }}}
> succeeds. (If someone finds that this is a different problem, please put
> in a separate ticket, but I'm guessing it's related.)
New description:
The following fails
{{{
sage: R.<x,y> = PolynomialRing(QQ)
sage: S = R.fraction_field()
sage: S(pari((x+y)/y))
TypeError: no canonical coercion from Fraction Field of Multivariate
Polynomial Ring in x, y over Rational Field to Rational Field
}}}
However, if you replace (x+y)/y with x+y, it works (in other words,
polynomials work but rational functions don't).
--
Comment (by pbruin):
In newer Sage versions (for example 5.13.beta0), the example
`S('(x+y)/y')` works correctly, but the original example (converting from
PARI) still fails.
--
Ticket URL: <http://trac.sagemath.org/ticket/11368#comment:3>
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