subring

Usage:
    <subring f K
defines an ideal K IN THE CURRENT RING R such that
    R/K = subring generated by f in the basering of f.
Parameters:
            f = 1xn matrix over some ring S.  The degrees of the
entries of f must be proportional to the degrees of the first
ncols f variables in the current ring.
Output values:
            K = ideal in the current ring
    This script calls pushforward1 to do set up the ring of the
correspondence defined by f,
R \tensor S modulo (xi-fi), where the xi are the
variables of R, and eliminate the variables of S
R and S may be quotient rings.