Re: How do you read this code ?

Barbara Morris wrote:

I bet they meant to code the equivalent of this

IF NOT
( (TTBAST = 'D' and TTA9CD = '001')
or TTA9CD = '002'
or TTA9CD = '003'
or TTA9CD = '012'
or TTA9CD = '013'
or (TTBAST = 'H' and TTA9CD = *blanks)
)

but they didn't understand DeMorgan's Law, so they just changed all the EQ's to NE's.

Charles' observation makes sense too. I tend to think the many compares of TTA9CD go with the TTBAST = 'D', but unless you know what the business goal is, it's hard to tell. That's why comments are essential, no matter how "readable" you make your code. Document the business requirement, not the operations.

I think the best way of coding NOT(complex expression) in fixed form RPG is to code it as an IF, and then use the ELSE to get the equivalent of NOT.
C TTBAST IFEQ 'D'
C TTA9CD ANDEQ '001'
C TTA9CD OREQ '002'
C TTA9CD OREQ '003'
C TTA9CD OREQ '012'
C TTA9CD OREQ '013'
C TTBAST OREQ 'H'
C TTA9CD ANDEQ ' '
* Empty "IF" section. We want the opposite of this IF
C ELSE
C MOVE TTOFCD OFCD 2
C ENDIF

I've seen this on more than one occasion, and while my natural tendency is to "fix" it, the truth is that running a statement through DeMorgan sometimes leaves you with code that has no resemblance to the initial goal, and that's really not much of a fix, is it?

But since that code is so old, I'm sure Joe's replacement is the correct one, since that's how it's been working.

I noticed it right away because I've got an old school upbringing, heavy on assembly language and boolean logic. That sort of stuff should still be mandatory, though, because no matter what tools you use, eventually you have to write business logic, and when you boil it down to its lowest level, *all* computing is ON and OFF. If you don't understand that level of code, you'll eventually get bitten by it.

Joe