begin
comment statement 'is' for calculation of object type;
	record RPoint (integer x, y);
	
	record RInt(integer n);
	reference(RPoint, RInt) r;

	r := RPoint;
	if r is RInt then write("RInt");
	
	r := RInt; comment memory lost?; 
	if r is RInt then write("RInt");
	
	r := null;
	if r is RPoint then write("RPoint");
end.