(*
 * rev-examples.sml
 * Dave Kauchak
 *
 * Some example sml functions playing with
 * function variants for reversing lists
 *
 *)

(* version 1.0 of reverse *)
fun rev []      = []
  | rev (x::xs) = (rev xs) @ [x];

(* 
 * our interval function from before for 
 * testing rev with large lists 
 *)
fun interval m n = 
    if n <= m then
        []
    else
        m::(interval (m+1) n);

fun revAux (acc, [])    = acc
  | revAux (acc, x::xs) = revAux (x::acc, xs);

fun rev2 lst = revAux ([], lst);

(* version 2.0 that uses an auxiliary function *)
fun rev2 lst =
    let
        fun revAux (u,[])   = u
          | revAux (u,x::xs) = revAux (x::u,xs);
    in
        revAux ([],lst)
    end;