Re: Difference between RPG III and RPG IV with CHAIN

[Vern Hamberg <vhamberg@xxxxxxxxxxx>]

Loyd

I am with you here - personal preference, of course, so we are ALL right!

I separate SETLL/CHAIN from the various READ* because you use a 
different BIF to test results. %found() (or %equal()) vs %eof(). So if 
I'm going to loop through multiple records, I'm inclined to SETLL and if 
%equal(), then READE and then a DOW not %eof() with another READE as the 
last item in the DO block. Perhaps with the non-priming technique of DOU 
%eof() and READE followed by IF %EOF(), there seem to be 2 tests instead 
of 1 at each pass - not so big a deal, maybe, but still... Maybe the 
compiler optimizes it, but I don't know that. As I think about it, it 
seems related to a principle I like to follow - don't do unnecessary 
repeated actions inside a loop.

JMNSHO
Vern

lgoodbar@xxxxxxxxxxxxxx wrote:
> It "reads" wrong to me. To me CHAIN implies an intent to retrieve one
> row and only one row, while SETxx/READE implies an intent of reading a
> group of rows (1+). I also do not like mixing CHAIN as the prime and
> READx as the looping construct. It looks like a mixed metaphor.
>
> It's more personal preference than anything, likely due to starting with
> RPG/IV (mid-1990s). 
>
> Thanks,
> Loyd
>
> "If we hit that bull's eye, the rest of the dominoes will fall like a
> house of cards. Checkmate." --Zapp Brannigan
>
>
>
>
> -----Original Message-----
> From: midrange-l-bounces@xxxxxxxxxxxx
> [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Tom Liotta
> Sent: Saturday, November 28, 2009 4:20 AM
> To: midrange-l@xxxxxxxxxxxx
> Subject: Re: Difference between RPG III and RPG IV with CHAIN
>
> Loyd Goodbar wrote:
>
>   
> > IMO, chain is the wrong tool for looking at files with duplicate keys.
> >     
> I've
>   
> > only used chain when key values are unique, or SETxx and READxx for
> > duplicate-keyed files. Know your data...
> >     
>
> Why? Especially for duplicate keys, CHAIN plus READE can work great. 
> The CHAIN not only does the SETLL but also a 'priming' READ for a 
> loop. Just wondering why it should be avoided.
>
> Tom Liotta
>
> p.s. Yes... late response. I'm almost at the point of "one list per 
> week".
>
>