RE: Suggested Technique -- RPG400-L

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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