ISO Pascal reference manual

END.
FOR w := sun TO fri DO writeln('day'); (not in range}
FOR w := 1 TO fri DO writeln('day'); (wrong type}
*ERROR 99 -- the final value cannot be assigned to
The final value of a FOR loop cannot be assigned to the loop control
variable < name > because it is not of a suitable type or not in the correct
range.
PROGRAM fail(output);
TYPE days = (sun, mon, tue, wed, thurs, fri, sat);
week = mon..fri;
VAR w : week;
BEGIN
END.
FOR w := mon TO sat DO writeln('day'); (not in range}
FOR w := mon TO 7 DO writeln('day'); [wrong type}
*ERROR 100 -- a procedure or function contains a statement which
threatens to alter the loop control variable
Note that this error is commuted into a warning if the EXTEND option is
specified.
The variable which is used to control the execution of a FOR statement
may not be used inside a procedure or function in such a way as to threaten
to alter it, even if the variable will not in fact be altered during the execution
of the loop.
PROGRAM fail(output);
VAR x : integer;
PROCEDURE proc;
BEGIN
END;
BEGIN
END.
X := 0 (this is the threatening statement}
FOR x := 1 to 10 DO writeln('hello'); [incorrect}
80 Pascal Issue 1