RE: Suggested Technique -- RPG400-L

I have no issue with Leave as an opcode and even use it from time to time. 
I have noticed though that generally after the exfmt mentioned in our
example we almost always have a select loop with the command keys,
validation, and entry choices.  Then we have an endsl.  In my experience it
is almost always confusing to have additional code after the endsl,  At that
point we have done whatever we intended to do and the subroutine really is
at a logical end.   

In other words, it makes my teeth itch when I see code after the endsl, so I
would only rarely face the dilema you mention.
 
---------------------------------
Booth Martin
http://www.martinvt.com
---------------------------------
-------Original Message-------
 
From: RPG programming on the AS400 / iSeries
Date: 01/31/05 15:16:28
To: RPG programming on the AS400 / iSeries
Subject: RE: Suggested Technique
 
Because with DOU you will keep processing until the ENDDO.  Why do all the
processing until the ENDDO when you can just LEAVE?
 
Michael Tobey
Applications Analyst
Foremost Farms USA
mike.tobey@xxxxxxxxxxxxxxxxx
IBM Certified AS/400 RPG IV Developer & RPG IV Programmer
 
 
 
-----Original Message-----
From: Booth Martin [mailto:booth@xxxxxxxxxxxx]
Sent: Monday, January 31, 2005 3:09 PM
To: RPG programming on the AS400 / iSeries
Subject: Re: Suggested Technique
 
 
While I understand the idea of DO *hival coupled with a leave, why not just
say it in the first place, and have a DOU F3 and avoid the extra lines of
coding?  DOU F3 is pretty clear, too, isn't it?
 
 
 
---------------------------------
 
Booth Martin
 
http://www.martinvt.com
 
---------------------------------
 
-------Original Message-------
 
 
 
From: RPG programming on the AS400 / iSeries
 
Date: 01/31/05 15:03:41
 
To: rpg400-l@xxxxxxxxxxxx
 
Subject: Re: Suggested Technique
 
 
 
Hi Alan,
 
 
 
<snip>
 
There are some brilliant programmers here, however, who advocate avoiding
 
use of the "iter" and "leave" op-codes. I find it hard to avoid using them
 
myself, but am still open on that issue.
 
</snip>
 
 
 
Now there's a statement! :-)
 
 
 
I would be VERY interested to hear the reasons why LEAVE and ITER have
 
entered the "Hall of Shame" along with CABxx and GOTO.
 
 
 
Personally, I find them very useful and would need a very, very hard sell to
 
convince me to stop using them. They do not preclude well structured code,
 
they have definite branching end-points, and they do not make code less
 
readable to a developer: All long-standing accusations levelled at CABxx and
 
GOTO.
 
 
 
For example - a classic screen loop:
 
 
 
// Display screen...
 
do *hival
 
 
 
exfmt screen
 
 
 
// If user presses F3, leave screen loop...
 
if F3_pressed
 
leave
 
endif
 
 
 
// Validate user input...
 
validateInput()
 
 
 
// If user enters invalid data, re-display screen, displaying error
 
message...
 
if userEntersInvalidData
 
iter
 
endif
 
 
 
// If user elects to update current valid data, update and leave screen...
 
if F8_update
 
updateData()
 
leave
 
endif
 
 
 
enddo
 
 
 
 
 
For me this code is simple - you can only leave the screen if you press F3
 
or update valid data. How do I know??? There's only two ways to leave the
 
screen - via the two LEAVE op-codes. If the code goes beyond the enddo then
 
F3 or F8 MUST have been pressed. In the case of F8, valid data MUST have
 
been entered. If the user enters invalid data then I force a re-display of
 
the screen (ITER) before any update code is reached - this forms a nice code
 
buffer, beyond which I am assured that the input data is valid.
 
 
 
I also prefer using "do *hival" because I do not want any "implicit" exits
 
of the loop. I want to see the exit strategy EXPLICITLY coded within the
 
screen loop. My time is more precious than the CPU cycle time. If I can
 
read/modify the code faster because there are large marker flags in front of
 
me then my company saves money. It's the old adage - KISS!
 
 
 
Just my preference.
 
 
 
Cheers
 
 
 
Larry Ducie
 
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