I think this is because the underlying computer algebra system Sage uses for univariate polynomial rings and multivariate rings are completely different, so support different operations.
Someone else might be able to suggest a work-round. John 2008/4/24 UAT <[EMAIL PROTECTED]>: > > For some reason, there is no covering morphism available for the > quotient ring QQ[X]/(X^2). But when I take the polynomial ring in two > variables, everything is fine: > > sage: R.<X> = PolynomialRing(QQ) > sage: S = R.quo(X^2) > sage: S > Univariate Quotient Polynomial Ring in Xbar over Rational Field with > modulus X^2 > sage: S.co (I pressed TAB here) > S.coerce_map_from S.coerce_map_from_impl > S.construction > sage: S.co > > And now: > sage: R.<X,Y> = PolynomialRing(QQ) > sage: S = R.quo(X^2) > sage: S > Quotient of Multivariate Polynomial Ring in X, Y over Rational Field > by the ideal (X^2) > sage: p = S.cover() > sage: p(X)*p(X) > 0 > sage: > > So, in two variables, everything is fine! > > My SAGE version is: > sage: version() > 'SAGE Version 3.0, Release Date: 2008-04-21' > > > > --~--~---------~--~----~------------~-------~--~----~ 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 URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
