Hi Dan,
You're right, this is a bug in the Laurent polynomial ring. The
underlying cause of the problem is this:
sage: P.<q> = LaurentPolynomialRing(QQ)
sage: qi = q^(-1)
sage: qi in P
False
sage: q in P
True
sage: P(qi)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/mike/<ipython console> in <module>()
/opt/sage/local/lib/python2.5/site-packages/sage/rings/polynomial/laurent_polynomial_ring.py
in __call__(self, x)
679 sage: L(1/2)
680 1/2
681 """
--> 682 return LaurentPolynomial_mpair(self, x)
683
/home/mike/laurent_polynomial.pyx in
sage.rings.polynomial.laurent_polynomial.LaurentPolynomial_mpair.__init__
(sage/rings/polynomial/laurent_polynomial.c:1889)()
/home/mike/multi_polynomial_libsingular.pyx in
sage.rings.polynomial.multi_polynomial_libsingular.MPolynomialRing_libsingular.__call__
(sage/rings/polynomial/multi_polynomial_libsingular.cpp:5984)()
/opt/sage/local/lib/python2.5/site-packages/sage/rings/rational_field.py
in __call__(self, x, base)
216 return x
217
--> 218 return sage.rings.rational.Rational(x, base)
219
220 def construction(self):
/home/mike/rational.pyx in sage.rings.rational.Rational.__init__
(sage/rings/rational.c:3321)()
/home/mike/rational.pyx in sage.rings.rational.Rational.__set_value
(sage/rings/rational.c:4494)()
TypeError: Unable to coerce q^-1 (<type
'sage.rings.polynomial.laurent_polynomial.LaurentPolynomial_mpair'>)
to Rational
I've made this the following ticket:
http://trac.sagemath.org/sage_trac/ticket/3617
--Mike
On Tue, Jul 8, 2008 at 4:02 PM, Daniel Bump <[EMAIL PROTECTED]> wrote:
>
>
> The following appears to me to be a bug. Shouldn't q^(-1) be
> in this Laurent polynomial ring?
>
> Dan
>
> sage: P.<q> = LaurentPolynomialRing(QQ)
> sage: type(q),type(q^(-1))
>
> (<type 'sage.rings.polynomial.laurent_polynomial.LaurentPolynomial_mpair'>,
> <type 'sage.rings.polynomial.laurent_polynomial.LaurentPolynomial_mpair'>)
> sage: q in P
> True
> sage: q^(-1) in P
> False
>
> >
>
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