(define-type list (datatype (cons car::int cdr::list) nil nil2)) (define l1::list) (define l2::list) (define l3::list) (define l4::list) (assert (= l1 l2)) (assert (= l1 nil)) (assert (= l3 l4)) (assert (= l3 nil2)) (assert (= l2 l4))