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From: abcscnuk@csuna.csun.edu (Naoto Kimura)
Newsgroups: comp.lang.pascal
Subject: Re: file windows (was Re: Standard Pascal)
Message-ID: <2100@csuna.csun.edu>
Date: 28 Jul 89 17:11:48 GMT
References: <8616@pyr.gatech.EDU> <18965@paris.ics.uci.edu> <SCHWARTZ.89Jul12023301@shire.cs.psu.edu> <4623@freja.diku.dk> <2929@virginia.acc.virginia.edu>
Reply-To: abcscnuk@csuna.csun.edu (Naoto Kimura)
Organization: CSU Northridge
Lines: 52

In article <2929@virginia.acc.virginia.edu> scl@virginia.acc.Virginia.EDU (Steve Losen) writes:
> ... (text deleted) ...
>while not eof do begin
>	if (input^ >= '0') and (input^ <= '9') then begin
>		read(number);
>		process(number);
>	end
>	else
>		get(input);
>end

You shouldn't inspect the file buffer before checking for eof.  It is
an error to access the file buffer if you are at the end of file.

procedure SkipJunk( ver f : text;  Legal : set of char );
    var
	done : boolean;
    begin
	if not eof(f) then
	    repeat
		if f^ in Legal then
		    done := true
		else begin
		    get(f);
		    done := eof(f)
		  end
	    until done
    end;

Also, you can't inspect the file buffer to see if you're at the end of
a line.  According to standard, you'll end up seeing a space.  The end
of line marker is just that - a marker and not necessarily a character.

Interactive I/O in pascal is a pain in the neck because pascal wasn't
designed to be interactive.  On some implementations, I've encountered
problems if too many calls were made to eof or eoln when doing
interactive I/O (it would lose characters).  I've had to do silly things
like force flushing of the buffer by outputting enough null characters
to fill the output buffer in some compilers.

>I admit that for most programming languages it is possible to come up
>with simple and elegant solutions to selected bizarre problems.  Too
>bad there isn't one language that is universally applicable.
>-- 
>Steve Losen     scl@virginia.edu
>University of Virginia Academic Computing Center

                //-n-\\			 Naoto Kimura
        _____---=======---_____		 (abcscnuk@csuna.csun.edu)
    ====____\   /.. ..\   /____====
  //         ---\__O__/---         \\	Enterprise... Surrender or we'll
  \_\                             /_/	send back your *&^$% tribbles !!