PROCEDURE Selection(choices$[],prompt$->sel$)
   IF UBOUND(choices$,1)-LBOUND(choices$,1)=0 THEN
      sel$=""
      EXIT PROCEDURE
   END IF
   ret$=""
   REPEAT
      FOR i=LBOUND(choices$,1) TO UBOUND(choices$,1) DO
         PRINT(i;": ";choices$[i])
      END FOR
      PRINT(prompt$;)
      INPUT(index)
      IF index<=UBOUND(choices$,1) AND index>=LBOUND(choices$,1) THEN ret$=choices$[index] END IF
   UNTIL ret$<>""
   sel$=ret$
END PROCEDURE