Returns the ring in which the coefficients lie

i1 : R = QQ[x] o1 = R o1 : PolynomialRing |

i2 : D = diffOp{x => 2*x^2} 2 o2 = 2x dx o2 : DiffOp |

i3 : ring D o3 = R o3 : PolynomialRing |

If the DiffOp was created using diffOp(RingElement) (e.g. after running makeWeylAlgebra), the ring