(* An interpreter for arithmetic expressions *)

exception Error of string

datatype Token 
  = INT of int
  | PLUS
  | TIMES
  | LPAREN
  | RPAREN
  
fun parseE (INT i :: ts) k = 
      parseE' ts k
  | parseE (LPAREN :: ts) k = 
      parseE ts (fn (RPAREN :: ts) => parseE' ts k
                  | _ => raise Error ") expected")
and parseE' (PLUS :: ts) k =
      parseE ts k
  | parseE' (TIMES :: ts) k = 
      parseE ts k
  | parseE' ts k = 
      k ts

val R = parseE ([INT 5, PLUS, INT 10, TIMES, LPAREN, INT 199, PLUS, INT 1, RPAREN])
        (fn [] => ()
          | _ => raise Error "expected EOF found something else");