RE: CHAIN Versus SETLL and READ When Data Needed

There are times when LEAVE and ITER are the best solution.
I don't use them alot, but this instance it seemed appropriate.

The Destination of a LEAVE in this type of situation in NOT implicit.
By definition, it will exit the loop.  It is not near as drastic as a GOTO.

Sharon


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of Dunfee, Randy
Sent: Wednesday, February 28, 2007 3:20 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: CHAIN Versus SETLL and READ When Data Needed


I would prefer that the LEAVE opcode had never been added.  IMHO, it is
EVEN WORSE than a GOTO because the destination is implicit.

I believe that when I see a conditioned DOU loop or a DOW loop that I
have the right to expect that the ONLY way out of this loop is to meet
the stated condition, and I can therefore skip desk-checking the "loop"
code if that particular condition is not of interest to me.  Is that
REALLY too much to ask?    


Randy

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Sharon Wintermute
Sent: Wednesday, February 28, 2007 4:07 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: CHAIN Versus SETLL and READ When Data Needed


Shannon, 

I have come to the point where i nearly HATE if with nested else groups.

I have started going this route.

DOU (wExit = Yes);
        SETLL all three
        if %Equal;
           Leave;
        Endif   ;
        SETLL 2 keys
        if %Equal;
          Leave;
        Endif;
        setll 1 key

        Leave;
Enddo;

This way i always have the status
If I need to know which file I add a flag. 

wExit is never set anywhere in the routine.  Its only used as a way to
loop.


Sharon

   The program logic is such that you check the maximum number of keys
for a match down to the minimum number of keys



    Like this:



             Key1    Klist

                         Kfld              Fld1

                         Kfld              Fld2

                         Kfld              Fld3



             Key2     Klist

                         Kfld              Fld1

                         Kfld              Fld2



             Key3     Klist

                          Kfld             Fld1





  Which one of these logic blocks is most efficient?



  Key1   Setll   file

      If    %FOUND(file)

              Key1   READE file

                      Use Fields

      Else

         Key2    Setll  File

           If   %FOUND(file)

                    Key2 Use Fields

          Else

            Key3  Setll File

                 If   %FOUND(file)

                    Key3 READE file

              Endif

           Endif

         Endif







OR....



              KEY1  Chain file

                         If       %FOUND(file)

                             Use fields

                        Else

             KEY2   Chain  file

                         If      %FOUND(file)

                             Use Fields

                         Else

             KEY3   Chain file

                         If   %FOUND(file)

                            Use Fields

                        Endif

                        Endif

                        Endif





My opinion is that the CHAIN is more efficient from both a
coding/maintenance standpoint and from an I/O standpoint, but I'm open
to opinions.











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