Singular

LIB "ncrat.lib";
ncInit(list("x", "y", "z"));
ncrat f = ncratFromString("x");
ncrat g = ncratFromString("y");
ncrep q = ncrepGet(f);
ncrep r = ncrepGet(g);
ncrep s1, s2;
s1 = ncrepMultiply(q, r);
print(s1);
==> lvec=
==> 0,0,0,1
==> 
==> mat=
==> 0, 0, x, -1,
==> 0, 1, -1,0, 
==> y, -1,0, 0, 
==> -1,0, 0, 0  
==> 
==> rvec=
==> 0,
==> 0,
==> 0,
==> 1 
s2 = q * r;
print(s2);
==> lvec=
==> 0,0,0,1
==> 
==> mat=
==> 0, 0, x, -1,
==> 0, 1, -1,0, 
==> y, -1,0, 0, 
==> -1,0, 0, 0  
==> 
==> rvec=
==> 0,
==> 0,
==> 0,
==> 1