Hi Simon, thanks a lot for your remarks. My expression doesn't contain I and thus the definition of I as the generator of CC doesn't change anything.
Well, the definition of f contains a lot of symbolic variables, so that might be the problem. I don't define f at once, but succesively. Starting with the fraction T12*T22*Z21*Z22/T1*T2*Z21+T1*T2*Z22, I replace successively all symbolic variables by expressions with new siymbolic variables, so that f grows larger and larger. Is there a possibility to have coefficients of symbolic variables and to work over the quotient field of complex numbers at the same time.? Thanks a lot in advance, Urs Hackstein 2011/10/20 Simon King <[email protected]> > Hi Urs, > > On 20 Okt., 13:08, Urs Hackstein <[email protected]> wrote: > > f.parent() gives indeed "Symbolic Ring". But at the beginning I defined > > > > P.<s> = CC[] > > P.fraction_field() > > Then we really need to know how you define f. > > Recall that in the other thread on that subject, I pointed out how > easy it is to start with a polynomial and end with a symbolic > expression: The symbol "I" is a symbolic expression. It is recognised > as an element of CC, but nevertheless its parent is the symbolic ring: > > sage: I in CC > True > sage: I.parent() > Symbolic Ring > > Hence, when you add the generator s of the polynomial ring with I, > then you obtain a symbolic expression, not a polynomial, even though > the sum is recognised as an element of the polynomial ring: > sage: P.<s> = CC[] > sage: s.parent() > Univariate Polynomial Ring in s over Complex Field with 53 bits of > precision > sage: (s+I).parent() > Symbolic Ring > sage: s+I in P > True > > This can be avoided by explicitly defining "I" to be the generator of > CC: > sage: I = CC.0 > sage: I > 1.00000000000000*I > sage: (s+I).parent() > Univariate Polynomial Ring in s over Complex Field with 53 bits of > precision > > Best regards, > Simon > > -- > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/sage-support > URL: http://www.sagemath.org > -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
