// this example explores forward declarations of classes, not just functions, which is what most blog posts cover.

#include "c.h"

#include "d.h"

struct B;

struct A {

B * a3; // this works because it is a pointer and doesn't need to know the full structure of the object pointed too.

B a2; // todo: Is it possible to make this work? // ERROR: field has incomplete type 'B'

};

struct B {

// A b2 {};

int i;

};

int main()

{

A my_a;

B my_b;

C my_c;

D my_d;

return 0;

}