[M N] res-div K 
 matrix M, N, K ; Each element of M and N must be an element of a ring.
 coker(K) is isomorphic to M/N. 
Example: [(x,y) ring_of_differential_operators 0] define_ring 
   [[[(x+x^2+y^2).] [(x y).]] [[(x+x^2+y^2).] [(x y).]]] res-div
res*div accepts string inputs, too. For example,
 [[[[(x+x^2+y^2)] [(x y)]] [[(x+x^2+y^2)] [(x y)]]]
   [(x) (y)]]  res*div ::
See also res-toString, res-setRing.

Nobuki Takayama 2020-11-24