(*
adapted to Oberon-07 by 0CodErr, KolibriOS team
*)
(*
There are 100 doors in a row that are all initially closed.
You make 100 passes by the doors.
The first time through, visit every door and toggle the door (if the door is closed, open it; if it is open, close it).
The second time, only visit every 2nd door (door #2, #4, #6, ...), and toggle it.
The third time, visit every 3rd door (door #3, #6, #9, ...), etc, until you only visit the 100th door.
What state are the doors in after the last pass? Which are open, which are closed?
*)
MODULE Doors;
IMPORT In, Out, Console;
CONST
CLOSED = FALSE;
OPEN = TRUE;
TYPE
List = ARRAY 101 OF BOOLEAN;
VAR
Doors: List;
I, J: INTEGER;
BEGIN
Console.open;
FOR I := 1 TO 100 DO
FOR J := 1 TO 100 DO
IF J MOD I = 0 THEN
IF Doors[J] = CLOSED THEN
Doors[J] := OPEN
ELSE
Doors[J] := CLOSED
END
END
END
END;
FOR I := 1 TO 100 DO
Out.Int(I, 3);
Out.String(" is ");
IF Doors[I] = CLOSED THEN
Out.String("Closed.")
ELSE
Out.String("Open.")
END;
Out.Ln
END;
In.Ln;
Console.exit(TRUE)
END Doors.