help with a snippet

[yamokosk]

Alright, i have starred at this for sometime, and while i could try every combination of const modifier, I would rather get an explanation why this won't go. I still get hung up on const stuff...

Matrix& Matrix::operator = (const Matrix& m) {
	if (*this == m) {
		for (int r = 0; r < rows(); r++) {
			for (int c = 0; c < cols(); c++) {
				(*this)(r,c) = m(r,c);
			}
		}
		return *this;
	} else {
		throw std::invalid_argument("Error! Matricies must be equal for assignment.");
	}
}

I get the following error on compile:

error C2662: 'cols' : cannot convert 'this' pointer from 'const class Matrix' to 'class Matrix &'
Conversion loses qualifiers
error C2662: 'rows' : cannot convert 'this' pointer from 'const class Matrix' to 'class Matrix &'
Conversion loses qualifiers

Thanks in advance!

[Paul McKenzie]

The error refers to cols() and rows(), but you didn't post what these are. I get no errors with the following code:

class Matrix
{
  public:
       int nRows;
       int nCols;
       int rows() const { return nRows; }
       int cols() const { return nCols; }
  
       Matrix& operator = (const Matrix& m);
};

Matrix& Matrix::operator = (const Matrix& m)
{
    int r = rows();
    return *this;
}

Regards,

Paul McKenzie

[yamokosk]

I apologize for the incompleteness of my problem, but I thought it had to do with something i did wrong in that function. Here were the original definitions for that class (exactly as you had guessed):

in header file:

public:
int rows() {return m_nRows;};
int cols() {return m_nCols;};

private:
int m_nRows, m_nCols;

So now i have modifed rows() and cols() to match yours and everything works perfectly. So correct me if I am wrong, but placing the const in rows() and cols() function makes what rows() and cols() pass back const?

Thanks for the assisstance!