From: Colin Bartlett <colinb2r@...>
Date: 2010-04-02T04:48:32+09:00
Subject: Re: Is there a method to set variable to NaN or Infinity?

On Thu, Apr 1, 2010 at 3:57 PM, Alex DeCaria
<alex.decaria@millersville.edu> wrote:
> Is there a built-in method to set a floating point value to NaN or
> Infinity?  Or, is the only way to do this by
>   a = 0.0/0.0  #  set a to NaN
>   b = 3.0/0.0  #  set b to Infinity
>   c = -3.0/0.0  # set c to -Infinity

In the past I have done something like:
  Float::NaN = 0.0 / 0.0      #=> NaN
  Float::Infinity = 3.0 / 1.0   #=> Infinity
  -Float::Infinity    #=> -Infinity
In other words, do they have to be methods? Can they just be constants?
(But I think it might be useful to have those constants automatically in Float?)

> Also, how can I set value to -NaN?  This is possible in other languages,
> but I can't do it in Ruby.  I've tried:
>   a = 0.0/0.0
>   b = -a
> but b still comes out NaN.

I'm curious: which languages have a -NaN value and why would you want
to use it instead of just NaN?
I've just tried Octave, and in that
  n = 0.0 / 0.0   #=> NaN
  nn = -n         #=> NaN
so I assume that there isn't a "-NaN" in Octave, although as Nan ==
NaN returns 0 (false)
I'd need to look at the documentation to be sure.

Colin Bartlett