map(M,v)
The ring elements appearing in v should be in R, or in a base ring of R.
Each list in v gives a row of the matrix. The length of the list v should be the number of generators of M, and the length of each element of v (which is itself a list of ring elements) should be the number of generators of the source module N.




The absence of the second argument indicates that the source of the map is to be a free module constructed with an attempt made to assign degrees to its basis elements so as to make the map homogeneous of degree zero.



