Singular

LIB "olga.lib";
ring R = 0,(x,y,Dx,Dy),dp;
def S = Weyl();
setring S; S;
==> // coefficients: QQ
==> // number of vars : 4
==> //        block   1 : ordering dp
==> //                  : names    x y Dx Dy
==> //        block   2 : ordering C
==> // noncommutative relations:
==> //    Dxx=x*Dx+1
==> //    Dyy=y*Dy+1
poly g1 = x+3;
poly g2 = x*y;
list L = g1,g2;
vector frac = [g1*g2, 17, 0, 0];
print(invertLeftFraction(frac, 0, L));
==> [17,x^2*y+3*x*y]
ideal p = x-1, y;
frac = [g1, x, 0, 0];
print(invertLeftFraction(frac, 1, p));
==> [x,x+3]
intvec rat = 1,2;
frac = [g1*g2, y, 0, 0];
print(invertLeftFraction(frac, 2, rat));
==> [y,x^2*y+3*x*y]