Why is destructor being called??

Hello all,

I have created a dynamic matrix class. I overloaded the multiplication operator as follows:

Code:

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Matrix Matrix::operator*(const Matrix &another) const //'const' keyword after => doesn't
{                                                                                                                //modify data members
        if (col != another.row)
        {
                cout<<"Error in matrix multiplication. Matrix dimensions do not agree."<<endl;
                return *this;
        }

        Matrix prod(row,another.col);
        Complex sum(0,0);

        for(int i=0; i<row; i++)                //i: 0 to 3
        {
                sum = 0;
                for(int j=0; j<another.col; j++)        //j: 0 to 2
                {
                        for(int k=0; k<row; k++)
                        {
                                sum = sum + A[i][k] * another(k,j);
                        }
                        //cout<<"prod("<<i<<","<<j<<") = "<<sum<<endl;
                        prod(i,j) = sum;
                }
        }
        return prod;
}

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I wanted to do it in such a way that if I do

Code:

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Matrix A(5,5), B(5,1);
//define the matrices
cout<<A*B<<endl;  //I overloaded the cout operator as well

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Just for the record, I created a complex number class, and I have defined a similar function:

Code:

---

Complex Complex::operator +(const Complex &num) const
{
        Complex sum;
        sum.real = real + num.real;
        sum.imag = imag + num.imag;
        return sum;                               
}

---

When I do

Code:

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Complex a(1,1), b(2,-2);
cout<<a+b<<endl;

---

The destructor is called after it is displayed. But this does not work for the Matrix class, and I just can't figure out why. I thought I would save you all the trouble of going through all the code by only displaying what is pertinent. If you need all the code, pls let me know. Thanks

Bill

Bill u was suppose to post this on C++ form not in here. showing a bit more code of your would help us

ssharish2005

Oh I'm sorry. I must have came here by mistake. Thanks.

C++ is a 'by value' language. The variable 'prod' is a local variable. Thus, the local copy is destroyed when the function ends, and it returns a copy of it. Thus, the destructor of 'prod' is called; it also creates a new copy, and returns it. Or at least I believe that's what's happening. I don't use C++ really ever.


Quzah.

But why is it working with the Complex function and not with the matrix function?

You're saying that on this line:

Code:

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sum = sum + A[k] * another(k,j); // In your overloaded operator*

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the destructor is never called on the variable in your operator+? Nor is it called on the two temp variables in your operator*?

http://cboard.cprogramming.com/showthread.php?t=77147