Question

Let’s say I have this:

struct coor
{
   int x;
   int y;
   COORD operator=(coor c)
   {
      COORD C={c.x,c.y}
      return C;
   }
}

and I needed to do:

coor c={0,0};
COORD C=c;

I could add operator overloading to coor, but how do you do that to return to left side?

Answer 1

Operator = must assign values to members of the object itself. The return value is there just to make a = b = c and similar things work. In your case it is irrelevant. Also, if you have A = B, the = defined in A will be used and if you have B = A, the = in B is used.
What you need is to write a = in COORD that takes coor parameter and updates members of this.

And the following does not call operator=:

COORD C=c;

It calls a matching constructor.

and the operator= MUST return *this for things like this: a=b=c=d to work but this is conventional