I could reproduce it!
sage: Q=FractionField(QQ['x'])
sage: x=Q.gens()
sage: V=Q['z']
sage: z=V.gen()
sage: x+z
<type 'exceptions.TypeError'>: unsupported operand parent(s) for '+':
'<type 'tuple'>' and 'Univariate Polynomial Ring in z over Fraction
Field of Univariate Polynomial Ring in x over Rational Field'
A missing automatic coercion! Should be trivial to fix now.
Michel
On May 17, 5:47 pm, "William Stein" <[EMAIL PROTECTED]> wrote:
> 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?
>
> Nothing -- You have found a subtle bug in SAGE's coercion code.
> If you make the coercion that is going on in the last line very explicit,
> then the above line works, e.g., this works (note that I've used some
> more compact notation at the beginning, but it's equivalent to
> what you wrote):
>
> {{{
> R.<a,b,c,d,e> = QQ[]
> 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+Ky([jg])
> phipoly
> ///
> y^3 + (-3*c^2 + 9*b*d - 36*a*e)*y + -2*c^3 + 9*b*c*d - 27*b^2*e -
> 27*a*d^2 + 72*a*c*e
>
> }}}
>
> The difference is that I put Ky([jg]) explicitly instead of jg.
>
> Whatever is causing this is a serious bug, and I hope somebody fixes
> it soon (or that I do). It's trac #365:
> http://www.sagemath.org:9002/sage_trac/ticket/365
>
>
>
>
>
> > 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 |
>
> > This message has been checked for viruses but the contents of an attachment
> > may still contain software viruses, which could damage your computer system:
> > you are advised to perform your own checks. Email communications with the
> > University of Nottingham may be monitored as permitted by UK legislation.
>
> --
> William Stein
> Associate Professor of Mathematics
> University of Washingtonhttp://www.williamstein.org
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