{

define shorter = fn(l1, l2) [ if da-equal?(l1, emptylist) 
                              then l1
                              else if da-equal?(l2, emptylist) 
                                   then l2
			           else if da-equal?( da-shorter( da-cdr(l1),
					   		          da-cdr(l2)),
						      da-cdr(l1))
				        then l1
				        else l2 ];

da-shorter( da-list(1, 2, 3), da-list(1, 2) );

define fib = fn(n) [ if (1 equal? n) then 1 else if (2 equal? n) then 1
                     else da-+( da-fib( (n - 1)), da-fib( (n - 2)) ) ];

da-list( da-fib(1), da-fib(2), da-fib(3), da-fib(4), da-fib(5), da-fib(6) );
}