/*
* Implementation of SUM operation
*/

/* call sum for every element of row */
sumOperation(L1,L2,SUM):-!,maplist(sumRows,L1,L2,SUM).

/* sum elements */
sumRows(H1,H2,H):-!,H is H1+H2.

/* main SUM function */
sum(SET1,SET2,SUM):-!,
    rowCount(SET1,RS1),
    rowCount(SET2,RS2),
    colCount(SET1,CS1),
    colCount(SET2,CS2),
    (RS1 == RS2 ->  /* same column and row count for sum  */
        (CS1 == CS2->
            maplist(sumOperation,SET1,SET2,SUM); /* map operation for every row of matrixes */
            SUM=false);
        SUM=false).