Question

This is a very basic operator overload question.
Say I had a class like this…

class xy
{
    public:
    double x, y;
    XY(double X, double Y) { x = X; y = Y;}
    XY operator+(const XY & add) const {
        return XY(this->x + add.x, this->y + add.y);
    }
    XY & operator+=(const XY & add) const {?}
    }
}

And I want operator+= do to what its supposed to do (you know, add to the current value of x and y). Wouldn’t the code be the same for operator+ and operator +=?

Answer 1

Yep, do the add operation (stick to the += operator), and return a reference to itself. Oh, and this can’t be a const method.

XY & operator+=(const XY & add) {
   this->x += add.x;
   this->y += add.y;
   return *this;
}