rank Module -- compute the rank

rank Module -- compute the rank

Synopsis:

Function: rank -- compute the rank

Input:

an instance of class Module.

Code:

     -- ../../../Macaulay2/m2/modules.m2:409-417
     rank Module := M -> (
          if isFreeModule M then numgens M 
          else if degreeLength ring M === 0 and isField ring M then numgens prune M
          else (
               f := poincare M // poincare ring M;
               T := (ring f)_0;
               substitute(f,{T=>1})
               )
          )