(* Copyright 2007 Ken Friis Larsen <ken@friislarsen.net> *)

let codes = 
    [("A",".-");   ("B","-..."); ("C","-.-."); ("D","-.."); ("E","."); 
     ("F","..-."); ("G","--.");  ("H","...."); ("I","..");  ("J",".---"); 
     ("K","-.-");  ("L",".-.."); ("M","--");   ("N","-.");  ("O","---"); 
     ("P",".--."); ("Q","--.-"); ("R",".-.");  ("S","..."); ("T","-"); 
     ("U","..-");  ("V","...-"); ("W",".--");  ("X","-..-");("Y","-.--"); 
     ("Z","--..")]
     
let rec decode (input : string) =
    if input = "" then { -> input }
    else { for c, code in codes when input.StartsWith code
           for rest in decode(input.Substring(code.Length)) 
           -> c + rest }

let test s code =
    if Seq.exists (fun x -> x = s) (decode code) then
        printf "%s can be decoded as %s\n"  code s
    else
        printf "%s can NOT be decoded as %s\n" code s

let _ = let start = System.DateTime.Now in
        let res = Seq.length(decode "...---..-....-...----") in
        printf "%f\n" ((System.DateTime.Now - start).TotalSeconds);;

(*
let _ = test "SOFIASOF" "...---..-....-...---..-.";;
let _ = test "SOPHIA" "...---..-....-";;
let _ = test "EUGENIA" "...---..-....-";;
*)