trace Matrix -- trace of a matrix

trace Matrix -- trace of a matrix

Synopsis:

Function: trace -- trace of a matrix

Input:

an instance of class Matrix.

Output:

an instance of class RingElement.

Code:

     -- ../m2/multilin.m2:118-123
     trace Matrix := RingElement => f -> (
          if rank source f != rank target f
          or not isFreeModule source f
          or not isFreeModule target f
          then error "expected a square matrix";
          sum(rank source f, i -> f_(i,i)))