Singular

7.10.6.28 ncrepRegularZeroMinimize

Usage:

ncrep s = ncrepRegularZeroMinimize(q, l);

Return:

ncrep s representing the same rational
function as ncrep q, where s is of minimal size

Assumption:

q is regular at zero, i.e.,
if one substitutes in 0 for all nc variables in q then q.mat has to be invertible

Note:

list l = list(x1, ..., xn) has to consist
exactly of the nc variables occuring in q

LIB "ncrat.lib";
ncInit(list("x", "y"));
ncrat f = ncratFromString("inv(1+x*y-y*x)");
ncrep q = ncrepGet(f);
ncrepDim(q);
==> 11
ncrep s = ncrepRegularZeroMinimize(q, list(x, y));
ncrepDim(s);
==> 3
s;
==> lvec=
==> 0,1,0
==> 
==> mat=
==> 1, y, 0, 
==> -x,1, -y,
==> 0, -x,1  
==> 
==> rvec=
==> 0, 
==> -1,
==> 0  
==>