class A {
  int x, y;

 

  void copy (in A a) {
    x = a.x;
    y = a.y;
  }

 

  void dump (string s) {
    writefln( "%s.A = { %s, %s }", s, x, y);
  }
}

 

class B : A {
  int z;

 

  void copy (in B b) {
    super.copy( b);
    z = b.z;
  }

 

  void dump (string s) {
    super.dump( s);
    writefln( "%s.B = { %s }", s, z);
  }
}

 

void main () {
  B foo = new B;
  B bar = new B;

 

  foo.x = 3;
  foo.y = 5;
  foo.z = 17;

 

  bar.x = 7;
  bar.y = 11;
  bar.z = 13;

 

  foo.dump( "foo");
  bar.dump( "bar");

 

  bar.copy( foo);
  bar.dump( "bar#2");
}

 

Which prints: