let rec
    append = lambda a. lambda b.
             if null a then b
             else (hd a) :: (append (tl a) b),
    listeq = lambda x. lambda y.
             if null x then null y
             else if null y then false
             else (hd x = hd y) and (listeq  tl x  tl y)
in list lv
   st   listeq (append (hd lv) (tl lv))
               (1 :: (2::nil))