I am having a problem with overloading an operator within a class structure. Below is the program that illustrates my problem. It defines a class Matrix, creates two matrices and multiplies them.

I created to multiplication functions. The first is a straight function, the second uses the overloaded * operator. The two methods produce different results.

```
#include <fstream.h>
class Matrix
{
private:
int ROWS, COLUMNS;
double *M;
public:
Matrix() { }; //default constructor
Matrix(int R, int C){ROWS=R; COLUMNS=C; M=new double[ROWS*COLUMNS];}; //constructor
~Matrix() {delete[] M;}; // destructor
int rows() {return ROWS;}
int cols() {return COLUMNS;}
void set(int R, int C) {ROWS=R; COLUMNS=C; M=new double[ROWS*COLUMNS];};
void m (int R, int C, double V) {M[R*COLUMNS+C]=V;};
double m (int R, int C) {return M[R*COLUMNS+C];};
void dump() {for (int r=0; r<ROWS; r++) {for (int c=0; c<COLUMNS; c++)
cout << M[r*COLUMNS+c]<< " "; cout << endl;};};
void dump(fstream &fout) {for (int i=0; i<(ROWS*COLUMNS); i++)
{fout << M[i]; if (i!=(ROWS*COLUMNS-1)) fout << ", ";};};
Matrix operator * (Matrix &);
};
Matrix Matrix::operator* (Matrix &B)
{
Matrix C;
double ans;
C.set(rows(), B.cols());
for (int r=0; r<rows(); r++)
for (int c=0; c<B.cols(); c++)
{
ans=0;
for (int i=0; i<cols(); i++)
ans=m(r,i)*B.m(i,c)+ans;
C.m(r,c,ans);
};
return(C);
};
void multiply(const Matrix &A, const Matrix &B, Matrix &C) //This Works!! Or at least seems to
{
double ans;
C.set(A.rows(), B.cols());
for (int r=0; r<A.rows(); r++)
for (int c=0; c<B.cols(); c++)
{
ans=0;
for (int i=0; i<A.cols(); i++)
ans=A.m(r,i)*B.m(i,c)+ans;
C.m(r,c,ans);
};
};
void main()
{
Matrix A(4,3);
Matrix B(3,6);
Matrix C;
A.m(0,0,11); A.m(0,1,12); A.m(0,2,13);
A.m(1,0,21); A.m(1,1,22); A.m(1,2,23);
A.m(2,0,31); A.m(2,1,32); A.m(2,2,33);
A.m(3,0,41); A.m(3,1,42); A.m(3,2,43);
B.m(0,0,11); B.m(0,1,21); B.m(0,2,31); B.m(0,3,41);B.m(0,4,51);B.m(0,5,61);
B.m(1,0,12); B.m(1,1,22); B.m(1,2,32); B.m(1,3,42);B.m(1,4,52);B.m(1,5,62);
B.m(2,0,13); B.m(2,1,23); B.m(2,2,33); B.m(2,3,43);B.m(2,4,53);B.m(2,5,63);
C=A*B;
A.dump(); cout << endl;
B.dump(); cout << endl;
C.dump(); cout << endl;
multiply(A,B,C);
A.dump(); cout << endl;
B.dump(); cout << endl;
C.dump(); cout << endl;
cout << "Done.\n";
}
```

The "multiply" function produces the correct output, but the overloaded * method does not. That method produces:

4.13e-306 794 1154 1514 1874 2234

794 1454 2114 2774 3434 4094

1154 2114 3074 4034 4994 5954

1514 2774 4034 5294 6554 7814

This answer is mostly correct. Only the (0,0) cell is wrong, it should be 434.

I have no idea what's going wrong here, other than I am getting the wrong answer.

While I could just use the "multiply" function, I suspect that my problem here may be more than just with the overloaded operator.

Most documentation examples don't seem to cover classes of matrices -- so I may have errors on several levels here.

Any advice, or suggestions, will be greatly appreciated.

Thanks,

Tom