Returns the sum of the coefficients of the specified matrix. 
- Template Parameters
 - 
  
    | T | type of the matrix of vector. Can be either a var matrix or matrix of vars.  | 
  
   
- Parameters
 - 
  
    | x | Specified var_value containing a matrix or vector.  | 
  
   
- Returns
 - Sum of coefficients of matrix. 
 
Definition at line 48 of file sum.hpp.