RE: RPG400-L Digest, Vol 5, Issue 636

Hello Adam,

Here is what I remember learning in collage about the difference between
Nested If's and a Case statements.

Case is easier to read -- but it evaluates the entire statement.
Nested If's are harder to read, but if the condition of the first
statement is meet then it does not evaluate the rest of the If's.

Now, this was 20 years ago and performance was a big concern. I guess
everyone is going for readability now.

That is my two cents.


-----Original Message-----
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Sent: Thursday, May 25, 2006 2:24 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: RPG400-L Digest, Vol 5, Issue 636

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Today's Topics:

   1. RE: Having both if/else executing at the same time
      (Willie J. Moore)
   2. RE: Having both if/else executing at the same time
      (AGlauser@xxxxxxxxxxxx)
   3. RE: Having both if/else executing at the same time (Rex Capio)
   4. RE: Having both if/else executing at the same time
      (Michael_Schutte@xxxxxxxxxxxx)


----------------------------------------------------------------------

message: 1
date: Thu, 25 May 2006 12:50:23 -0700
from: "Willie J. Moore" <WMoore@xxxxxxxxxxxxxxx>
subject: RE: Having both if/else executing at the same time

Joe,
Tried it 'elseif'. That did not work. Then put it back the way it was
and low and behold it worked. We have compaired the two codes and they
look the same. 
I would like to think everyone for there help and comments.
Willie...

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of AGlauser@xxxxxxxxxxxx
Sent: Thursday, May 25, 2006 12:36 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: Having both if/else executing at the same time


Willie,

Have you stepped through the code?  Any new information to pass on?


Joe,

I'm interested in your reasons for using select/when over if/elseif.  I 
think I prefer if/elseif only because I learned about them first, and to

me case-like statements should fall through like they do in C.  It seems

redundant to me to have both structures behave identically, and awkward
to 
have to do:

if (A)
  // do A stuff
endif;

if (B);
  // do B stuff
endif;

if (NOT (A OR B));
  // some sort of error
endif;

when what I'd like to do is:

select;
   when A;
      // do A stuff

   when B;
      // do B stuff
      leave;
 
   other;
      // some sort of error

endsl;

I realize that you're not advocating one method over the other, but I've

heard people say that it is 'better' to use select/when instead of 
if/elseif, but they never provide any good reasons.  Do you have any, or

does it just feel more natural the way if/elseif does to me?

Adam


rpg400-l-bounces@xxxxxxxxxxxx wrote on 25/05/2006 02:53:47 PM:

> Actually, the original code simply selected among three mutually 
exclusive
> conditions.  Using an ELSEIF doesn't change the outcome at all.
> 
> IF CondA;
>   DoA;
> ELSE;
>   IF CondB;
>     DoB;
>   ELSE;
>     DoC;
>   ENDIF;
> ENDIF;
> 
> Is functionally equivalent to:
> 
> IF CondA;
>   DoA;
> ELSEIF CondB;
>   DoB;
> ELSE;
>   DoC;
> ENDIF;
> 
> The ELSEIF just removes the second "endif" (which you accidentally
left 
in
> your post, Bob, LOL!).  This is also functionally equivalent to:
> 
> SELECT;
>   WHEN CondA;
>     DoA;
>   WHEN CondB;
>     DoB;
>   OTHER;
>     DoC;
> ENDSL;
> 
> Nowadays I tend towards the third form if there are more than two 
mutually
> exclusive conditions.
> 
> It should be noted that the three conditions being selected among are
> (CondA), ((NOT CondA) and (CondB)), and finally ((NOT CondA) and (NOT
> CondB)).  That is, even if both CondA and CondB are true, only the
first
> branch of the code will be executed.
> 
> Joe
> 
> 
> > From: Bob Cozzi
> > 
> > ELSE and IF are two statements. In your code the only time the
second 
IF
> > will be
> > performed is when the first IF fails. Why? Because the first ELSE is

only
> > going
> > to be run if the first IF fails. Otherwise it'll jump to the ENDIF
> > statements.
> > I think what you really mean to have is ELSEIF not "ELSE" and "IF".
> > Replace the ELSE and IF with ELSEIF, and then take a look as this 
page:
> > 
> > www.rpgiv.com/blueribbon.html
> > 
> >   if %len(%trim(APIErrMsg)) > 0;
> >      W#ERFL = *ON;
> >      W#MSDT = 'Error #' + APIErrMsg + ' receiving data from ' +
> >               'data queue.  Detail:  ' + APIErrDta;
> >    elseif %trim(itmInfo) = '';
> >       W#ERFL = *ON;
> >       W#MSDT = 'Invalid data received from data queue: ' +
> >             itmInfo ;
> >    else;
> >        uMATNO = jMATNO;
> >        uSIZE = jSIZE;
> >        uTEMPER = jTEMPER;
> >        uINSUL = jINSUL;
> >        uTENSIL = jTENSIL;
> >    endif;
> >    endif;
> 
> 
> -- 
> This is the RPG programming on the AS400 / iSeries (RPG400-L) mailing 
list
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