(define (list->assoc lis)
(cond
;((and (proper-list? lis) (> (length lis) 2))
((and (pair? lis) (> (length lis) 2))
(cons (list (car lis) (cadr lis)) (list->assoc (cddr lis)))
)
;((and (proper-list? lis) (= (length lis) 2))
((and (pair? lis) (= (length lis) 2))
(list lis)
)
(else lis)
)
)