MODULE ackerman;

IMPORT  ASCII, NumConv, InOut;

VAR     m, n            : LONGCARD;
        string          : ARRAY [0..19] OF CHAR;
        OK              : BOOLEAN;

PROCEDURE Ackerman (x, y   : LONGCARD) : LONGCARD;

BEGIN
  IF    x = 0  THEN  RETURN  y + 1
  ELSIF y = 0  THEN  RETURN  Ackerman (x - 1 , 1)
  ELSE
    RETURN  Ackerman (x - 1 , Ackerman (x , y - 1))
  END
END Ackerman;

BEGIN
  FOR  m := 0  TO  3  DO
    FOR  n := 0  TO  6  DO
      NumConv.Num2Str (Ackerman (m, n), 10, string, OK);
      IF  OK  THEN
        InOut.WriteString (string)
      ELSE
        InOut.WriteString ("* Error in number * ")
      END;
      InOut.Write (ASCII.HT)
    END;
    InOut.WriteLn
  END;
  InOut.WriteLn
END ackerman.