{

 open Lexing p;

 exception LexicalError of string

 fun lexerError lexbuf s = 
     raise LexicalError (s);

    (* [` ` `\t` `\n` `\r`]  { Token lexbuf } *)

}

rule Token = 
  parse
    [`0`-`9`'a'-'f''A'-'F']+            { case Int.fromString "0x" ^ (getLexeme lexbuf) of
                               NONE   => lexerError lexbuf "internal error"
                             | SOME i => BYTE i
                          }  
  | ['+'                  { PLUS  }
  | eof                   { EOF   }
  | _                     { lexerError lexbuf "Illegal symbol in input" }
;