Usage:
<rmap vars values f
Create a ring map which sends the ith element of the ideal "vars"
(which must be a variable) to the ith element of the ideal "values".
All other variables are sent to zero.
Parameters:
vars = 1xn matrix of (distinct) variables, with base ring R
values = 1xn matrix of polynomials over the ring S
Output values:
f = 1xm matrix over S, where m is the number of variables of R.
This script is useful since the variables don't have to appear "in
order". It is also useful in scripts where you don't know the names
of variables in advance.
Caveats: If an entry of "vars" is not a variable, the initial term is
used. This initial term should be a variable.