Ilya Zakharevich on Wed, 7 Nov 2001 13:27:12 -0500 |
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Re: subst() broken |
On Tue, Nov 06, 2001 at 04:37:24PM +0100, Bill Allombert wrote: > (1+y)*Mod(1,P(z)) is a polynomial, belonging to the ring {Q[z]/P(z)Q[z]}[y] > > Mod(1+y,P(z)) is a coset, belonging to the quotient ring Q(z)[y]/P(z)Q(z)[y], > which is isomorphic to the null ring since P(z) is invertible in Q(z)[y] > > > The next question is how I can deduce that these expressions will > > result in elements of these rings. [Preferably deduce basing on the > > documentation. ;-] > > You can probably *deduce* it... with some effort :-) > Please read > ?? POL > ?? POLMOD > and > ??"Multivariate objects"@4 I did. Many times. With a very low yield. > The big thing is that each polynomial euclidean division is done as univariate > polynomials division in the higher priority variables, because euclidean division > does not make sense for multivariate polynomials. IMO, what is needed is some explicit explanation; with ample crosslinks to it from all the places which mention POLMOD and variable priorities... Ilya