RE: definintion of signed integer?

["Koester, Michael" <mkoester@xxxxxxxxxxxxx>]

Thanks Charles and Alan.
I found that the unsigned PositiveValue was indeed causing issues.  Changing PositiveValue to 3i  0 (option 1)
Alleviated the problem.  Leaving PositiveValue at 3u  0 and using the assignment " NegativeValue = %int(PositiveValue) - 21;"  (2a)
still threw MCH1216, even with the values in the original example.   Hmmm.

(You'd think a business language should be a bit more forgiving in basic math functionality, but my expectations are often unrealistic) 

-Michael


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Monday, September 27, 2010 4:38 PM
To: RPG programming on the IBM i / System i
Subject: Re: definintion of signed integer?

I'm pretty sure you're being bit by eval's handling of intermediate results...

Since PositiveValue is an unsigned integer, and 21 is a constant that
could also be considered an unsigned integer, eval is treating the
results as an unsigned integer which obviously won't hold a negative
value.

Solution:
1) redefine PositiveValue as a signed integer
2) let eval know you're dealing with signed values
    a) NegativeValue = %int(PositiveValue) - 21;
    b) NegativeValue = PositiveValue +  (-21);

note that 2a) would blow up given a PositiveValue greater than 127.

I'd go with option 1) myself....

HTH,
Charles



On Mon, Sep 27, 2010 at 4:04 PM, Koester, Michael
<mkoester@xxxxxxxxxxxxx> wrote:
> I have a variable defined "3i 0", local to a subprocedure that I expect
> could be any whole number value from -128 to +127, per my understanding
> of a signed integer.  When my subprocedure puts what I expect to be a
> minus 18 into the field, I get the dreaded "MCH1216 -  too small to hold
> result" crash & burn.
>
> I'm sure I can fix it instantly by defining packed numerics, but I need
> to understand the rules.
>
> D PositiveValue            3u  0
> D NegativeValue            3i  0
>  /free
>  PositiveValue = 3;
>  NegativeValue = PositiveValue - 21;
>   [down in flames we go]
>  /end-free
>
> What could be so tough about subtracting 3 from 21 and expecting -18?
> Please set me straight here.  It's an SQLRPGLE program on a 6.1 box.
>
> Many thanks.
> Michael Koester
>
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