OpenEuphoria

RE: Uninitialized Variables

• Posted by Chris Bensler <bensler at mail.com> Mar 23, 2002
• 464 views

Andy Serpa wrote:
> 
> > > > 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?
> 

Apparently NAN is (silly me) Not A Number! :P
using equal() compares NAN properly and consistently

Here is my revised uninitialized values for variables:

   integer  = -INF
   atom     =  INF
   sequence =  NAN
   object   = -NAN

Chris