OpenEuphoria

RE: Uninitialized Variables

• Posted by Chris Bensler <bensler at mail.com> Mar 24, 2002
• 457 views

Andy Serpa wrote:
> 
> > If you don't mind me asking, what sorts of expressions are
> > your genes coming up with that yield NAN? Are you using
> > INF on occasion? Or square root of negative numbers? I'm
> > asking because, while this needs to be addressed (and so
> > far the discussion is very revealing,) it might save you time
> > if a workaround can be found.
> > 
> 
> I have simple checks to avoid division by zero, taking the log of a 
> negative, etc., but if you mix a bunch of random mathmatical functions 
> with a bunch of random values, you're going to get some strange results 
> sometimes.  The checks I have are all for *before* a function is 
> performed.  For instance, if the second argument is zero in a division, 
> don't do the calculation.  This will avoid an outright crash.  Other 
> functions, like tan(), will output nan or -nan if the value going in is 
> too extreme.  Since it doesn't actually crash, it would be much easier 
> to check for a nan after the function is performed then try to set 
> strict limits that must be checked before each individual function is 
> performed.  If I can check for nans reliably, I can just set up a custom 
> 
> "non_nan" type that catches it (a type that always returns TRUE to avoid 
> 
> a crash, but sets another global flag so I can throw out that function 
> internally)...
> 
> 

I still don't understand what is wrong with equal(x,nan)


Chris