dec map : (alpha -> beta)#list alpha -> list beta
--- map(f, nil)   <= nil
--- map(f, a::al) <= (f a)::map(f, al)

zip x = hd x=()->()
        map hd x:zip(map tl x)

letref x,y = x,y
in if x > y loop x := x - y
   if x < y loop y := y - x
   else x;;

max :- returns the largest element
max [a] = a
max [a,b] = a, a >= b
          = b
max (a:x) = max [a,max x]

let rec type * list <=> () + * # ( * list)
        with nil = abslist(inl ()) 
        and  cons x l = abslist(inr(x,l))
        and  null l = isl(replist l) 
        and  hd l = fst(outr(replist l))
        and  tl l = snd(outr(replist l));

rec type Tree *a = empty + node (Tree *a) *a (Tree *a)

let fact_iter n =
    let acc = ref 1 in frec n where rec
    frec = function 0 -> !acc | n -> acc:=!acc*n; frec(n-1)

dec map : (alpha -> beta)#list alpha -> list beta
--- map(f, nil)   <= nil
--- map(f, a::al) <= (f a)::map(f, al)

zip x = hd x=()->()
        map hd x:zip(map tl x)

letref x,y = x,y
in if x > y loop x := x - y
   if x < y loop y := y - x
   else x;;

max :- returns the largest element
max [a] = a
max [a,b] = a, a >= b
          = b
max (a:x) = max [a,max x]

let rec type * list <=> () + * # ( * list)
        with nil = abslist(inl ()) 
        and  cons x l = abslist(inr(x,l))
        and  null l = isl(replist l) 
        and  hd l = fst(outr(replist l))
        and  tl l = snd(outr(replist l));

rec type Tree *a = empty + node (Tree *a) *a (Tree *a)

let fact_iter n =
    let acc = ref 1 in frec n where rec
    frec = function 0 -> !acc | n -> acc:=!acc*n; frec(n-1)