Having two structs refer to each other's variables in C++ - c++

Question

I have two different structs which I want to convert to each other like this:
PointI a = PointI(3,5);
PointF b = a;
I assume that I will need to do something like the code below:
struct PointF
{
PointF operator=(PointI point){
x = point.x;
y = point.y;
return *this;
}
float x, y;
};
struct PointI
{
PointI operator=(PointF point)
{
x = point.x;
y = point.y;
return *this;
}
int x, y;
};
But the problem is that PointF uses PointI before it is declared. From what I've read in other questions, I understand that I can declare PointI before defining both structs, and then use a pointer. Though it seems that I won't be able to access the variables x and y from that pointer, as these are not defined yet.
Is there a way I can add these variables to the struct declaration before defining them? Or is there a better way to solve this problem?

Answer 1

First, forward declare one of the structs and fully declare the other. You'll need to use either a reference or pointer for the forward declared type, since the compiler doesn't have its definition yet:
struct PointI;
struct PointF
{
PointF operator=(const PointI& point);
float x, y;
};
Next, you need to fully declare the struct you forward declared:
struct PointI
{
PointI operator=(const PointF& point);
int x, y;
};
Now you can go ahead and define the operator= functions for each:
PointF PointF::operator=(const PointI& point)
{
x = point.x;
y = point.y;
return *this;
}
PointI PointI::operator=(const PointF& point)
{
x = point.x;
y = point.y;
return *this;
}
Note that you should change your operator= functions to return references rather than copies, but that's outside the scope of this question/answer.