fix conversion of GAP univariate rat functions, which are polynomial with valuation>0

[dimpase]

sage: x = libgap.Indeterminate(libgap.Integers, "x")                                                              
sage: x.sage()                                                                                                    
1

oops. This is due to

sage: (2*x).CoefficientsOfUnivariateRationalFunction()                                                                
[ [ 2 ], [ 1 ], 1 ]

where 3rd 1 is valuation v, so that the function is x^v(2/1)=2x.
But the corresponding code added in #21020

if self.IsUnivariatePolynomial():
    from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing
    R = PolynomialRing(base_ring, var)
    return R(num)

forgets about the case of valuation>0.

CC: @fchapoton @tscrim

Component: interfaces

Author: Frédéric Chapoton

Branch/Commit: c582e80

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/30496

[dimpase]

comment:1

discovered by chance, while working on #29314

[fchapoton]

Branch: u/chapoton/30496

[fchapoton]

Author: Frédéric Chapoton

[fchapoton]

comment:3

here is a proposal

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New commits:

82191ca

fix conversion from gap polynomial with valence > 0

[fchapoton]

Commit: 82191ca

[dimpase]

comment:4

could you write this x = libgap.eval('Indeterminate(Integers, "x")') (and the other place there where x is set) as

sage: x = libgap.Integers.Indeterminate('x')

This is less ugly.

[dimpase]

Changed branch from u/chapoton/30496 to public/packages/30496

[dimpase]

Changed commit from 82191ca to c582e80

[dimpase]

comment:5

OK, good.

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New commits:

c582e80

better syntax for libgap calls

[dimpase]

Reviewer: Dima Pasechnik

[vbraun]

Changed branch from public/packages/30496 to c582e80