Re: %EOF

(I'm not sure why I'm entering this debate... but...)

James, I agree with your opnion on loops.   I feel that the method
of the priming read is a better way to do it, it makes the actual
DOW loop do the work.

I've always thought it was silly to test the same condition twice,
or to defeat the actual looping mechanism by using LEAVE operations,
although in the real world, sometimes LEAVE it necessary due to
the complexity of your application, its best to try to avoid it.

A loop with a priming read will execute less actual operations while
the program is running, because it only tests the argument once per
iteration of the loop.

A loop where the read is done, and then a "LEAVE" statement is done
upon failure is somewhat misleading, because it'll say something like
"I'm going to do this until *IN10 is on" and then it doesn't actually
use THAT to determine how long it does it...    In fact, it wouldn't
change your program to say "DOW 1=1" instead of "DOW *IN10=*OFF"
since that'll always evaluate to TRUE...     And therefore, your
your ENDDO is nothing more than a GOTO back up to your DOW.

Another argument for the priming read logic is that the condition of
the loop is tested immediately after its SET.   You don't have to
search through the code to figure out if anything else might be
tampering with the variables in your DOW condition in between the
CHAIN/READE and the ENDDO.

(Okay, now I've gotten involved in this debate, too...  I must be
a glutton for punishment)




"James W. Kilgore" <qappdsn@ibm.net> wrote:
> Dan,
>
> I see your point, but LEAVE is nothing more than a GOTO of a differe
>  color.
>
> Nesting an IF within a DO is like a double negative.  You already ma
>  the test,
> why test twice?
> IMHO, that's why you'll find primed DOW loops with a bottom read so
>  common.
>
> First, the primed read determines if you need to enter the loop at
>  all, where a
> DOU will always perform the loop once, thereby necessitating the inn
>  IF.  Not to
> mention the propensity to throw in a GOTO aka LEAVE.
>
> It's a style thing.
>
> James W. Kilgore
> email@James-W-Kilgore.com
>
> P.S. I get a perverse kick out of the annual DOx debates that appear
>  on this list.
> =8^)
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