RE: IF Coding question

["Bob Cozzi" <cozzi@xxxxxxxxx>]

I agree, parens should be used to clarify things whenever possible.
I don't agree that negative conditional evaluations are "more
straightforward" than positive logic that is prefixed with NOT.
It is a known fact that the mind can interpret positive logic much quicker
than negative.  But, hey, we're not out to save the world with RPG IV, now
are we. :)
-Bob


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of M. Lazarus
Sent: Tuesday, March 30, 2004 7:41 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: IF Coding question

Bob,

  I'm not sure if it's mandated or not (w/o checking the order of 
evaluation in the manual), but the following would be the preferable way to 
mimic the original code:

    If       NOT ( TOT1a = TOT2a and TOT1b = TOT2bc )

  Although, my preference would be:

    If       TOT1a <> TOT2a Or TOT1b <> TOT2bc

  since it's more straightforward.

  -mark

At 3/30/04 06:39 PM, you wrote:
>It equates to this in RPG IV:
>
>    If       NOT TOT1a = TOT2a  and TOT1b = TOT2bc
>    EXCEPT   HEADR
>    EXCEPT   TOTAL
>    ENDIF
>
>It is an old "trick" in RPGIII that allows you to do a set of opcodes when
>something is NOT true. In other words, it is too hard to code the opposite
>condition, so they coded it in "positive logic" and use the ELSE to reverse
>the "polarity" of the conditional statement.
>-Bob Cozzi
>
>
>-----Original Message-----
>From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
>On Behalf Of simafrog
>Sent: Tuesday, March 30, 2004 8:19 AM
>To: RPG programming on the AS400 / iSeries
>Subject: IF Coding question
>
>I am trying to understand the point/reason for this code:
>       TOT1a   IFEQ TOT2a
>       TOT1b   ANDEQTOT2bC
>               ELSE
>               EXCPTHEADR
>               EXCPTTOTAL
>               ENDIF
>Why do you need the "IF" "AND" part? What purpose does this serve?

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