/* A program that prints the Frobenius product of two matrices A and B:  i.e. trace of the matrix transpose(A)*B. 
Demonstrating how to use the modulo % operator in accessing indices.
 */
#include <iostream>
using namespace std;


double Frob_product( double A[2][2], double B[2][2] ) 
   {
    
   double frob_product = 0.0;
   
  for (int i =0 ; i <2 ; ++i)
      {
      frob_product +=(A[i][i]*B[i][i] + A[i][(i+1)%2] *B[i][(i+1)%2]);
      
 // cout<< "a["<< i <<"]["<<(i+1)%2 <<"] = " << endl;
    for (int j=0; j<2; ++j)
      //cout<< "a["<< i <<"]["<<j <<"]  " ;
     cout << endl;
 }//for i-loop!


   return frob_product ;
 }//end of the Frobenius product function.
int main() {
    double A[2][2] ={ {1,2},{3,4} } ;
    double B[2][2] ={ {2,3},{-1,4} } ;
    cout<< "F product = "<<Frob_product(A,B)<< endl;
    return 0;
}