[Axiom-mail] Converting to and from partial fractions

[Alasdair McAndrew]

This is an example of where Axiom's handling of domains fries my limited brain.

ex:=z/(z-1)+2*z/(z-3)

(Result is returned as a single polynomial fraction.)

Now, what I want to do is to break this single fraction up into its original components.  The canonical way to do this (for my purposes), is to divide the fraction by z, form partial fractions, and multiply through by z.  Here goes:

exf:=partialFraction(ex/z::FRAC POLY INT,z)$PFRPAC(INT)

Now, because the result is returned as a partial fraction,if I try

nthFractionalTerm(exf,1)*z

I don't get 2*z/(z-3), but 2+6/(z-3).  So I need to remove this term from its partialFraction domain.

But none of nthFractionalTerm(exf,1)::FRAC POLY INT, nthFractionalTerm(exf,1)::EXPR INT seem to work.

Any ideas?

Thanks,
Alasdair