Jonathan Bryant wrote:

> All,
>
> I'm having to learn Scheme for a class, and I ran across a simple but  
> really useful predicate: amb.  More info on this can be found here:  
> http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z- 
> H-16.html#node_chap_14
>
> Since OCaml doesn't seem to have this, I implemented it:
>
> exception Amb
> let rec amb l = match l with
> | [] -> raise Amb
> | h::t -> try h () with Amb -> amb t
>
> let amb l = try Some (amb l) with Amb -> None
>
You might try:
let rec amb = function
    | [] -> None
    | h :: t ->
       let r =
          try
             Some(h ())
          with
             | _ -> None
       in
       match r with
       | None -> amb t
       | Some(_) as e -> e
;;

As a slightly better implementation.

Brian