OpenEuphoria

Re: math.e and misc.e

• Posted by Juergen Luethje <j.lue at gmx.??> Aug 06, 2007
• 481 views

Robert Craig wrote:

> Jason Gade wrote:
> > Is it possible to just be able to test for nan or -nan? And maybe to assign
> > nan in Euphoria source?
> 
> If you want something interesting to do,
> try setting a Euphoria constant to NaN, and see what
> you can do with it. You might have to use float64_to_atom()
> as you suggested, since things like sqrt(-1) are caught
> by the interpreter. Don't ask me what the bit pattern is.
> Also, I'm not sure how consistent the treatment of NaN is 
> across C compilers (e.g. printf()).

I have the following code in my private math library:

global function pos_inf()
   return 1.8e+307 * 10              -- Positive Infinity value (IEEE 754)
end function

global function neg_inf()
   return -pos_inf()                 -- Negative Infinity value (IEEE 754)
end function

global function nan()
   return -(pos_inf()+neg_inf())     -- "Not a Number" value    (IEEE 754)
                                     --   mulNAN = -(0*pos_inf())
end function                         --   divNAN = -(pos_inf()/pos_inf())

Jason, if you want to do some "research" you can look in the EUforum
archives for this stuff.

Previously, I had implemented the values above by assigning them to
global constants. But that caused a strange bug which was very hard to
find:
I had written a DLL that included my private math library, but did not
use these global constants. The DLL is a plugin for Total Commander (TC).
When trying to _install_ (not even use) this plugin by using the concerning
installation routine that is built-in into TC, then TC always crashed.
After moving 'pos_inf', 'neg_inf' and 'nan' from global constants to
global functions, the problem was gone.

Regards,
   Juergen