RE: Chain vs SetLL/ReadE

[Chandra Krieg <chandrak@xxxxxxxxxxxxxx>]

Since I am a new programmer...the RPG cycle is foreign to me!  Never even learned it and updating those programs are sometimes "interesting" for me!  This is one programmer you will be sure to never see the cycle from!  :) 

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of vhamberg@xxxxxxxxxxx
Sent: Tuesday, September 02, 2008 9:21 AM
To: RPG programming on the AS400 / iSeries
Subject: Re: Chain vs SetLL/ReadE

Chandra

I happen to prefer this style for reading records in a loop, because you need to test only one function - %eof(fielname) - to me it is just simpler and cleaner.

Now if I am testing existence, I'll use SETLL with %equal(filename).

If I want only the one record, I'll use CHAIN with %found(filename) - yes, I could use the loop method, but I guess CHAIN says more to me what I'm doing - sort of self-documenting the process.

But for a loop, I like the suggested form. Or you could always go with a PRIMARY file and use the cycle!!  Just kidding - maybe!

HTH
Vern

-------------- Original message --------------
From: Chandra Krieg <chandrak@xxxxxxxxxxxxxx> 

> Hello all,
>
> I have been told that the preferred method of random record retrieval 
> is to use the SetLL, then do a ReadE and check for the %EOF indicator.
>
> Why is this preferred over using a Chain with %found or even checking 
> for %Equal on the SetLL before reading the file? I have been told that 
> the Chain doesn't do what I'm expecting it to but I've never had issues in the past.
>
> I have read the archive posts and found opinions on the subject but no 
> concrete explenation as to why. As with some of the posts I don't 
> understand why you would want to readE the file if the SetLL didn't 
> find an %equal match or why if you plan to read the file a chain isn't appropriate.
>
> I'm being told to use the following code instead of a Chain. 
>
> SetLL (KeyFields) FIleName;
> ReadE (KeyFields FIleName;
> DoW Not %EOF(FIleName);
> do my stuff
> ReadE (KeyFields) FileName;
> EndDo;
>
> Any explanations would be helpful! 
>
> TIA! 
>
> Chandra Krieg
> i5 Programmer/Analyst
> RateWatch
> (P) 1.800.348.1831 ext 311
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