Re: Two reade loops: which one preferred ?

Maybe I'm being thick (it is Friday after all), but why the 'if %equal'?

This is how I code my reade loops:

/free
   Setll key format;
   Reade key format;
   Dow not %eof;
       Exsr Process;
       Reade key format;
   Enddo;
/end-free

Or am I missing something?

Peter Colpaert
iSeries Application Developer

Honda Europe NV
Langerbruggestraat 104
B-9000 GENT
Belgium
Peter.Colpaert@xxxxxxxxxxxx
Tel: +32 9 2501 334
Fax: +32 9 2501 231
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James Rich <james@xxxxxxxxxxx>
Sent by: midrange-l-bounces@xxxxxxxxxxxx
21/11/2003 09:57
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Subject
Re: Two  reade loops: which one preferred ?






On Fri, 21 Nov 2003, afvaiv wrote:

> Just for curiosity, some people will code it the #2 way, but WHY do MOST
> people seem to prefer #1 ?
>
> ----- Style #1 -------------------------------------------
> mykey setll record
> if %equal
> mykey reade record
> dow not %eof
> ... process ...
> mykey reade record
> enddo
> endif
>
> ----- Style #2 -------------------------------------------
>
> mykey setll record
> if %equal
> do *HIVAL
> mykey reade record
> if %eof leave
> ... process ...
> enddo
> endif

Here's my take on this that hopefully makes good sense.  Looking at the
typical C way:

while ((fscanf(outfile, "%c", &c))!=EOF)
{
   do stuff...
}

we notice that all the logic that determines when a loop is executed or
exited is in one place.  You can easily tell that the loop will be run
depending on fscanf() and will only exit when fscanf() reaches EOF.

RPG has more than one way to code in a similar way.  But I think the goal
should be to make it easily discernable what will cause the loop to
execute and what will cause it to exit.  Keep the logic that does that in
one place: at the top of the loop.  This makes it immediately obvious how
the loop is designed to work.  One way to keep that logic together is to
use Style #2 that you mention.

Style #1 does not keep the logic together and therefore does not make it
immediately obvious how the loop is designed to work.  For this reason I
feel that Style #1 is poor programming style and should be avoided.

James Rich





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