On 5/17/07, Prof. J. E. Cremona <[EMAIL PROTECTED]> wrote:
>
> Problem: when executing the following, the last line takes forever and
> had to be killed:
>
> R = PolynomialRing(QQ, ['a','b','c','d','e'], 5)
> K = R.fraction_field()
> a,b,c,d,e = K.gens()
>
> ig = 12*a*e-3*b*d+c^2
> jg = 72*a*c*e+9*b*c*d-27*a*d^2-27*e*b^2-2*c^3
> hg = 8*a*c-3*b^2
> deltag = 4*ig^3-jg^2
>
> Ky.<y> = PolynomialRing(K,'y')
> phipoly = y^3-3*ig*y+jg
>
> What am I missing?
I'm missing something too: I got a "division by zero" error but
don't see any denominators in the expressions.
sage: R = PolynomialRing(QQ, ['a','b','c','d','e'], 5)
sage: K = R.fraction_field()
sage: a,b,c,d,e = K.gens()
sage:
sage: ig = 12*a*e-3*b*d+c^2
sage: jg = 72*a*c*e+9*b*c*d-27*a*d^2-27*e*b^2-2*c^3
sage: hg = 8*a*c-3*b^2
sage: deltag = 4*ig^3-jg^2
sage:
sage: Ky.<y> = PolynomialRing(K,'y')
sage: phipoly = y^3-3*ig*y+jg
---------------------------------------------------------------------------
<type 'exceptions.ZeroDivisionError'> Traceback (most recent call last)
/Users/wdj/sagefiles/sage-2.5.alpha0/<ipython console> in <module>()
/Users/wdj/sagefiles/sage-2.5.alpha0/element.pyx in
element.RingElement.__mul__()
/Users/wdj/sagefiles/sage-2.5.alpha0/element.pyx in
element.ModuleElement._rmul_c()
/Users/wdj/sagefiles/sage-2.5.alpha0/polynomial_element.pyx in
polynomial_element.Polynomial._rmul_()
/Users/wdj/sagefiles/sage-2.5.alpha0/local/lib/python2.5/site-packages/sage/rings/polynomial_ring.py
in __call__(self, x, check, is_gen, construct, absprec)
173 x = list(x.Eltseq())
174 if absprec is None:
--> 175 return C(self, x, check, is_gen, construct=construct)
176 else:
177 return C(self, x, check, is_gen,
construct=construct, absprec = absprec)
/Users/wdj/sagefiles/sage-2.5.alpha0/local/lib/python2.5/site-packages/sage/rings/polynomial_element_generic.py
in __init__(self, parent, x, check, is_gen, construct)
718 class Polynomial_generic_dense_field(Polynomial_generic_dense,
Polynomial_generic_field):
719 def __init__(self, parent, x=None, check=True, is_gen =
False, construct=False):
--> 720 Polynomial_generic_dense.__init__(self, parent, x,
check, is_gen)
721
722
/Users/wdj/sagefiles/sage-2.5.alpha0/local/lib/python2.5/site-packages/sage/rings/polynomial_element_generic.py
in __init__(self, parent, x, check, is_gen, construct, absprec)
73 raise TypeError, "denominator must be constant"
74 else:
---> 75 x = x.numerator() * (~x.denominator()[0])
76
77 if isinstance(x, Polynomial):
/Users/wdj/sagefiles/sage-2.5.alpha0/rational.pyx in
rational.Rational.__invert__()
<type 'exceptions.ZeroDivisionError'>: rational division by zero
sage:
>
> John
>
> --
> Prof. J. E. Cremona |
> University of Nottingham | Tel.: +44-115-9514920
> School of Mathematical Sciences | Fax: +44-115-9514951
> University Park | Email: [EMAIL PROTECTED]
> Nottingham NG7 2RD, UK |
>
>
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> >
>
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