wrong operator() overload called
- by user313202
okay,
I am writing a matrix class and have overloaded the function call operator twice. The core of the matrix is a 2D double array. I am using the MinGW GCC compiler called from a windows console.
the first overload is meant to return a double from the array (for viewing an element).
the second overload is meant to return a reference to a location in the array (for changing the data in that location.
double operator()(int row, int col) const ; //allows view of element
double &operator()(int row, int col); //allows assignment of element
I am writing a testing routine and have discovered that the "viewing" overload never gets called. for some reason the compiler "defaults" to calling the overload that returns a reference when the following printf() statement is used.
fprintf(outp, "%6.2f\t", testMatD(i,j));
I understand that I'm insulting the gods by writing my own matrix class without using vectors and testing with C I/O functions. I will be punished thoroughly in the afterlife, no need to do it here.
Ultimately I'd like to know what is going on here and how to fix it. I'd prefer to use the cleaner looking operator overloads rather than member functions.
Any ideas?
-Cal
the matrix class: irrelevant code omitted
class Matrix
{
public:
double getElement(int row, int col)const; //returns the element at row,col
//operator overloads
double operator()(int row, int col) const ; //allows view of element
double &operator()(int row, int col); //allows assignment of element
private:
//data members
double **array; //pointer to data array
};
double Matrix::getElement(int row, int col)const{
//transform indices into true coordinates (from sorted coordinates
//only row needs to be transformed (user can only sort by row)
row = sortedArray[row];
result = array[usrZeroRow+row][usrZeroCol+col];
return result;
}
//operator overloads
double Matrix::operator()(int row, int col) const {
//this overload is used when viewing an element
return getElement(row,col);
}
double &Matrix::operator()(int row, int col){
//this overload is used when placing an element
return array[row+usrZeroRow][col+usrZeroCol];
}
The testing program: irrelevant code omitted
int main(void){
FILE *outp;
outp = fopen("test_output.txt", "w+");
Matrix testMatD(5,7); //construct 5x7 matrix
//some initializations omitted
fprintf(outp, "%6.2f\t", testMatD(i,j)); //calls the wrong overload
}
