(* left-associative fold *)
(* foldl : ('a * 'b -> 'a) -> 'a -> 'b list -> 'a *)
fun foldl f z [] = z
  | foldl f z (x::xs) = foldl f (f(z,x)) xs;
(* NB. The standard SML foldl seems to have the wrong type! *)

(* right-associative fold *)
(* foldr : ('a * 'b -> 'b) -> 'b -> 'a list -> 'b *)
fun foldr f z [] = z
  | foldr f z (x::xs) = f(x, (foldr f z xs))
(* equivalent to standard SML foldr *)


(* find the smallest value in an int list *)
fun smallestVal (x::xs) = foldl Int.min x xs;

(* find the position of the smallest value in an int list *) 
fun smallestPos (x::xs) =
  #2(foldl (fn ((i,p,v),x) => if v>x then (i+1,i,x) else (i+1,p,v))
           (1,0,x) xs)

(* -------------------------------------------------------e.g.-- *)
val xs = [10,11,12,9,10,11,9];
smallestVal xs;
smallestPos xs;
(* High-order functions,             LA, CSSE, Monash U., 7/2005 *)