If the ring of `M` is a base ring of `R`, then the matrix presenting the module will be simply promoted (see promote). Otherwise, a ring map from the ring of `M` to `R` will be constructed by examining the names of the variables, as described in `(map,Ring,Ring)` (missing documentation).

i1 : R = ZZ/101[x,y]; |

i2 : M = coker vars R o2 = cokernel | x y | 1 o2 : R-module, quotient of R |

i3 : M ** R[t] o3 = cokernel | x y | 1 o3 : R[t]-module, quotient of (R[t]) |