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LOOPDEMO.MOD
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1987-02-08
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(* Chapter 4 - Program 1 *)
MODULE LoopDemo;
FROM InOut IMPORT WriteString, WriteInt, WriteLn, Write;
CONST Where = 11;
VAR Index : INTEGER;
What : INTEGER;
Letter : CHAR;
BEGIN
WriteString("REPEAT loop = ");
Index := 0;
REPEAT
Index := Index + 1;
WriteInt(Index,5);
UNTIL Index = 5; (* This can be any BOOLEAN expression *)
WriteLn;
WriteString("WHILE loop = ");
Index := 0;
WHILE Index < 5 DO (* This can be any BOOLEAN expression *)
Index := Index + 1;
WriteInt(Index,5);
END;
WriteLn;
WriteString("First FOR loop = ");
FOR Index := 1 TO 5 DO
WriteInt(Index,5);
END;
WriteLn;
WriteString("Second FOR loop = ");
FOR Index := 5 TO 25 BY 4 DO
WriteInt(Index,5);
END;
WriteLn;
(* Note - The four loops above could use a CARDINAL type variable
in place of the INTEGER type variable Index. The next 2
examples must use an INTEGER type variable because it
must be capable of storing a negative value. *)
WriteString("Third FOR loop = ");
FOR Index := 5 TO -35 BY -7 DO
WriteInt(Index,5);
END;
WriteLn;
What := 16;
FOR Index := (What - 21) TO (What * 2) BY Where DO
WriteString("Fourth FOR loop = ");
WriteInt(Index,5);
WriteLn;
END;
(* Note - The next two loops are demonstrations of using a CHAR
type variable to index a FOR loop. *)
FOR Letter := "A" TO 'Z' DO
Write(Letter);
END;
WriteLn;
FOR Letter := 'z' TO 'a' BY -1 DO
Write(Letter);
END;
WriteLn;
(* Note - The following loop contains an EXIT which is a way to get
out of the loop in the middle. *)
Index := 1;
LOOP
WriteString("In the EXIT loop ");
WriteInt(Index,5);
IF Index = 5 THEN
WriteLn;
EXIT;
END;
WriteString(" We are still in the loop.");
WriteLn;
Index := Index + 1;
END;
END LoopDemo.