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From: ok@goanna.cs.rmit.edu.au (Richard A. O'Keefe)
Subject: Re: Leading zeros with Int_IO.Put()? Or another package?
Date: 1996/11/22
Message-ID: <573mrl$3v2$1@goanna.cs.rmit.edu.au>#1/1
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organization: Comp Sci, RMIT, Melbourne, Australia
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Date: 1996-11-22T00:00:00+00:00
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rav@goanna.cs.rmit.edu.au (robin) writes:

>	ok@goanna.cs.rmit.edu.au (Richard A. O'Keefe) writes:

>	>rav@goanna.cs.rmit.edu.au (robin) writes:

>	>>Now why would you bury a picture specification in a remote place from 
>	>>the output statement that uses it?

>	>In order to be close to the *variable declarations* it will be used with.

>That's back to front, isn't it!  A layout isn't
>used with variable declarations, it's used with I/O
>operations.  So it's logical that that's where it should >be.

Nope.  A layout is used to write *DATA*.  It's not "where is it going"
that determines what picture should be used, but "what am I writing".
COBOL got this right:  the picture is a property of the variable and
is declared with it.  (Well, nearly right.  But at least it's _better_.)

The point is that if I do
	DECLARE D DECIMAL(6,2);	/* +/- $9,999.99 */
and 4000 lines later have
	PUT (D) EDIT(P'$9999.99');
then some day I am going to _change_ the declaration of D to
	DECLARE D DECIMAL(8,2);
	    /*  Money; limit has been raised to +/- $999.999.99 */
but the picture is _not_ changed.
Better by far to have
	DECLARE D DECIMAL(6,2);	/* money */
	DECLARE D_PICTURE PICTURE ...whatever */
so that when the declaration of D is revised, the declaration of
D_PICTURE gets revised to match.

>I said "simpler" because that's exactly what it is.
>It's clear and simple.

I always thought the APL I wrote was clear and simple too.
_I_ knew what it meant.  Unfortunately, the APL system I was using
was not an IBM one, and didn't conform _exactly_ to the ISO APL
standard, and so the code didn't port very well because some of the
boundary conditions were just _slightly_ different, and some of the
things I'd used had no equivalent at all.

In the same way, the PL/I thing is "clear and simple"
 - IF you already know PL/I pictures (I found knowing COBOL pictures
   was the reverse of a help with PL/I pictures, because the details
   were different),
 - IF you were letter perfect about the boundary conditions and what
   picture editing does in unusual case, and
 - IF the code is never maintained.

In the same way, the formats in BASIC look really cute, but when you
try to port or revise your program, watch out!

-- 
Mixed Member Proportional---a *great* way to vote!
Richard A. O'Keefe; http://www.cs.rmit.edu.au/%7Eok; RMIT Comp.Sci.