From: james@...
Date: 2002-06-01T03:47:40+09:00
Subject: RE: Infinity (?!)

> This is exactly what I'm talking about: this is an arbitrary distinction
> imposed by the underlying processing mechanism.  The point I'm trying to
> illustrate is the lack of transitive logic between equalities:
>
>         1 == 1.0
>         1/0 == 1/0  (in that they both throw exceptions)
>         1/0.0 == 1/0.0

plus,

   0 == 0.0 # true
and

 0.0 == 0   # true


>
> but
>
>         0/0 != 0/0.0
>
> I don't see how this can be rationalized except by an appeal to
> "that's the
> way it has to be because of how computers work".

Which is a surprising, and unpleasant, coupling.

The Ruby 1.7 source has this, in numeric.c:

#if defined(__FreeBSD__) && __FreeBSD__ < 4
    /* allow divide by zero -- Inf */
    fpsetmask(fpgetmask() & ~(FP_X_DZ|FP_X_INV|FP_X_OFL));
#endif

Is this because some systems really *don't* let you divide by zero?


James