let tokenize (str : string) : pos tok list =
  let (toks, _, _) = List.fold_left
    (fun ((toks : pos tok list), (line : int), (col : int)) (tok : Str.split_result) ->
      match tok with
      | Delim t ->
         if t = " " then (toks, line, col + 1)
         else if t = "\t" then (toks, line, col + 1)
         else if t = "\n" then (toks, line + 1, 0)
         else if t = "(" then (LPAREN (line, col, line, col + 1) :: toks, line, col + 1)
         else if t = ")" then (RPAREN (line, col, line, col + 1) :: toks, line, col + 1)
         else
           let tLen = String.length t
           in ((TSym (t, (line, col, line, col + tLen))) :: toks, line, col + tLen)
      | Text t ->
         if t = "true" then (TBool (true, (line, col, line, col + 4)) :: toks, line, col + 4)
         else if t = "false" then (TBool (false, (line, col, line, col + 5)) :: toks, line, col + 5)
         else
           let tLen = String.length t
           in try ((TInt (int_of_string t, (line, col, line, col + tLen))) :: toks, line, col + tLen) with
              | Failure _ -> (TSym (t, (line, col, line, col + tLen)) :: toks, line, col + tLen)
    )
    ([], 0, 0)
    (full_split (regexp "[()\n\t ]") str)
  in List.rev toks
;;