REM Range extraction
DECLARE FUNCTION RangeExtract$ (RS$)

Range$ = " 0,  1,  2,  4,  6,  7,  8, 11, 12, 14, "
Range$ = Range$ + "15, 16, 17, 18, 19, 20, 21, 22, 23, 24, "
Range$ = Range$ + "25, 27, 28, 29, 30, 31, 32, 33, 35, 36, "
Range$ = Range$ + "37, 38, 39"
PRINT RangeExtract$(Range$)
END

FUNCTION RangeExtract$ (RS$)
  TS$ = "": I% = 0
  F% = VAL(RS$)
  DO
    I% = INSTR(I% + 1, RS$, ",")
    T% = VAL(MID$(RS$, I% + 1))
    IF T% = F% + R% + 1 THEN
      R% = R% + 1
    ELSE
      SELECT CASE R%
        CASE 0
          TS$ = TS$ + LTRIM$(STR$(F%)) + ","
        CASE 1
          TS$ = TS$ + LTRIM$(STR$(F%)) + "," + LTRIM$(STR$(F% + R%)) + ","
        CASE ELSE
          TS$ = TS$ + LTRIM$(STR$(F%)) + "-" + LTRIM$(STR$(F% + R%)) + ","
      END SELECT
      R% = 0: F% = T%
    END IF
  LOOP WHILE I% <> 0
  RangeExtract$ = LEFT$(TS$, LEN(TS$) - 1)
END FUNCTION