On 20 Jun 2013 20:24, Clay Carley wrote:
<<SNIP>> Stanley Myers' book, "RPG IV Programming on the AS/400".
I'm doing the programming assignments at the end of Chapter 5, and
assignment 5-2 wants "Include the control that prevents a
divide-by-zero error". As far as I can tell, this hasn't been
discussed in the book yet; so I don't want to jump ahead with a
solution that isn't what they are really looking for. <<SNIP>>
This is what the line in question could be something like:
C EVAL GRPFT = NETPRICE / GROSSPRFT
Is there some EVAL option I'm missing for this? Setting indicators
is discussed, but for the life of me I don't see anything related to
divide by zero.
The "control that prevents" might have been covered already within or
prior to the alluded topic of "Setting indicators"; having reached
whatever is the current point [Ch. 5] within the book. Have
_conditioned calculations_ been covered?
Conditioned calculations are available when using the fixed-form
C-spec Calculation Specifications as shown with "the line in question"
shown; i.e. non-free-form coding. Using a [non-control-level]
Conditioning Indicator, Positions 9-11, to effect the "Indicators
Conditioning Calculations" is described in the following page and then
two pages later, of the RPG Reference; possibly something also since
covered in the book being used:
http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/topic/rzasd/sc092508123.htm#wq165
Thus, an indicator can condition that line of code. Having
initialized the value of GRPFT to something reflecting an appropriate
overall effect in later calculations [e.g. perhaps initialized to zero],
along with previously having set an indicator to reflect the condition
of GROSSPRFT=0, that since-conditioned line of code would not be
executed. Having conditioned the line of code, the divide-by-zero could
be prevented by avoidance; i.e. avoiding performing the evaluation of
the expression, implicitly preventing an error MCH1211 and the RNQ0102.
If the /general indicator/ 10 [i.e. *IN10] reflects the dividend for
the expression is a zero-value, then the given line of code, as modified
below [as the second C-spec line], will not execute:
C EVAL *IN10 = ( grossprft = 0 )
C N10 EVAL GRPFT = NETPRICE / GROSSPRFT
I did some searching, but I found what I would logically do to check
for a zero in the variable before doing the math. That hasn't been
covered in this book yet, so I'm guessing there is something else to
it.
I was unsure if the above quoted text implies that the above EVAL to
set the *IN10 was what was found by effectively /looking forward/ in the
book, and thus implying something that was not yet covered... or if
perhaps implying that something else that was found "to check for a
zero". Considering the prominence of indicators however, I expect how
such an indicator could be set, would already have been covered by the
fifth chapter.
But for lack of mention of /conditioned calculations/ and their
conspicuous value in avoiding the error by avoiding the attempt to
evaluate the expression, plus a followup message seeming to imply that
what had been found [but was "not yet covered" in the book] was "IF
statements", I figured I would spell-it-out in my above reply. The
conditioned statement is just some obscure fixed-format conditional
logic as contrasted with the more conspicuous logical test of a
condition when predicated with the more visible OpCodes like IF.
midrange.com
