OpenEuphoria

RE: Uninitialized Variables

• Posted by Andy Serpa <renegade at earthling.net> Mar 23, 2002
• 436 views

> > > I tried to use NAN as well, but everything is equal to NAN!?
> > > NAN=1
> > > NAN=-NAN
> > > NAN=INF
> > > NAN=-5039487
> > > 
> > > Is that proper behaviour?
> > > 

I just ran into this problem yesterday -- how do you test for a nan?  It 
registers equal to everything if you use '=' but not equal().  The 
behavior also changes if you compile to C, and is different with every 
compiler.  This always works:

x = <nan>

if x and compare(x/x,1) then
 ...

(a nan passes the first test, which is neccessary to avoid div by zero 
for non-nans -- it also passes the second test, which for any real 
number will compare() to 0)

It also occured to be that the representation of a nan might be 
consistent if you atom_to_float() it, but I haven't tried that yet.  
Either way seems expensive -- is there a good way to test if something 
is a nan?