Re: Preventing a divide by zero error

Hi Chuck,

I think this might be what the book is looking for! "Conditioning indicators" have been discussed, but really only to the point of "they can be there", not what they do. In this chapter, they also discuss how to set indicators, or set variables to a default value. I'm sure if I was in a classroom, this topic would have been discussed in more detail.

Thank you very much! The only way to check my work is to see what comes off the printer. Whether I'm doing it correctly or not would have been really difficult in this case.

I very much appreciate all the other replies as well!

Clay Carley
Sonic.net/ Sonic Telecom



CRPence wrote:

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.