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From: filbo@gorn.santa-cruz.ca.us (Bela Lubkin)
Newsgroups: comp.lang.pascal
Subject: Re: file windows (was Re: Standard Pascal)
Message-ID: <1.filbo@gorn.santa-cruz.ca.us>
Date: 30 Jul 89 14:17:43 GMT
References: <2929@virginia.acc.virginia.edu>
Organization: R Pentomino
Lines: 58

In article <2929@virginia.acc.virginia.edu> scl@virginia.acc.Virginia.EDU
(Steve Losen) writes:
>Here's a good example of how convenient the file buffer variable is:
>
>Suppose you want to allow the user to input a bunch of integers, separated
>by any sequence of non-numeric characters.  For example, the following
>atrocity is legal input:
>
>,,100 ,20,
>,
>
>   30
>40,, 5050
>,,,
>
>The program should process the integers 100, 20, 30, 40, and 5050.
>Here is a trivial piece of Standard Pascal that does the job correctly.
>
>while not eof do begin
>	if (input^ >= '0') and (input^ <= '9') then begin
>		read(number);
>		process(number);
>	end
>	else
>		get(input);
>end
>
>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.

My experience with "Standard Pascal" is pretty ancient, but I think that
at least in this case you are fooling yourself.  The file buffer may be
"convenient", but you're not actually using it -- you commit to reading
the data whether or not it's a digit.  A >simpler< and >more< elegant
piece of Standard Pascal code that does the same thing is:

while not eof do begin
        read(number);
        if (number >= '0') and (number <= '9') then process(number);
           { else don't do anything, thus disposing of the invalid char }
end

In >most< situations where you might use the file buffer, it's not difficult
to store away the item in your own one-item buffer; in this case, not even
that is necessary.  There are also cases where the file buffer is really a
Good Thing; I'm not trying to excuse Turbo Pascal's unfortunate omission.
In general I think that there are very few places where a file buffer would
be more useful than true random access as in TP, and if TP wasn't
pretending to be Pascal I wouldn't mind the omission.  As it stands, it's
an annoying portability issue.

>Steve Losen     scl@virginia.edu
>University of Virginia Academic Computing Center

Bela Lubkin     * *   filbo@gorn.santa-cruz.ca.us    CIS: 73047,1112
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