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Tips and Techniques: Move Off of Resulting Indicators

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Something wonderful happened in OS/400 V4R2. IBM removed the requirement for resulting indicators from all opcodes except TEST and LOOKUP.

Why? Because IBM introduced a set of built-in functions that replaced the function of those old resulting indicators and opened RPG IV up to much more readable code. In fact, if IBM hadn't done this, creating the /FREE syntax would have been very difficult.

But time after time after time, I see new code being written that looks like this:

.....C*Rn01Factor1+++++++OpCode(ex)Factor2+++++++Result++++++++Len++DcHiLoEq
     C     CustNo        Chain     CustMast                           31
     C     *IN31         DowEQ     *OFF
      ** Blah, blah, blah
     C     CustNo        ReadE                                            31
     C                   enddo

Excuse me a second....

I'm sorry, I just gagged a little. It happens when I see this happening in new code today.

First, why DOWEQ? Is this 1985? No, it is 2005, so write 2005 code.

     C     CustNo        Chain     CustMast                           31
     C                   DOW       *IN31 = *OFF
      ** Blah, blah, blah
     C     CustNo        ReadE                                            31
     C                   enddo

Next, why use this silly trick with the resulting indicators? So many times, people put them in the wrong column or test for the wrong condition. In V4R2, the %FOUND and %EOF built-in functions were introduced.

.....C*Rn01Factor1+++++++OpCode(ex)Factor2+++++++Result++++++++Len++DcHiLoEq
     C     CustNo        Chain     CustMast
     C                   if        %Found()
     C                   DOU       %EOF()
      ** Blah, blah, blah
     C     CustNo        ReadE 
     C                   enddo
     C                   endif

When you CHAIN to a file, you can test for a "found" condition rather than the "not found" condition traditionally tested for when using indicators.

With any of the READ opcodes--READ, READE, READP, READPE--you can test for %EOF (end-of-file) condition.

Unfortunately, someone at IBM was a bit too anal when designing this, and the %FOUND built-in is not changed by any of the READ opcodes. So in a CHAIN followed by a READE, both %FOUND and %EOF have to be tested, as in my example above.

The point here is that there is absolutely no reason to continue to use resulting indicators. Use the built-in functions and make your code more readable.

Bob Cozzi is a programmer/consultant, writer/author, and software developer of the RPG xTools, a popular add-on subprocedure library for RPG IV. His book The Modern RPG Language has been the most widely used RPG programming book for nearly two decades. He, along with others, speaks at and runs the highly-popular RPG World conference for RPG programmers.

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