[Haskell-cafe] Re: 0/0 > 1 == False

[Achim Schneider]

David Roundy <droundy at darcs.net> wrote:

> On Thu, Jan 10, 2008 at 09:41:53PM +0100, Achim Schneider wrote:
> > David Roundy <droundy at darcs.net> wrote:
> > > On Thu, Jan 10, 2008 at 09:24:34PM +0100, Achim Schneider wrote:
> > > > John Meacham <john at repetae.net> wrote:
> > > > > 1/0 = Infinity
> > > > > -1/0 = -Infinity
> > > >
> > > > Just out of curiosity:
> > > > 
> > > > 1/-0 = -Infinity?
> > > > -1/-0 = Infinity?
> > > 
> > > Yes.  (You could have tried this for yourself, you know... but I
> > > suppose haskell-cafe isn't a bad interactive Haskell interpreter,
> > > perhaps more user friendly than ghci.)
> >
> > Prelude> 1 `div` 0
> > *** Exception: divide by zero
> > 
> > That's it. One just shouldn't just extrapolate and think you didn't
> > mean GHC but IEEE...
> 
> Prelude> 1/(-0)
> -Infinity
> 
> You need to use the / operator, if you want to do floating-point
> division.
>
Yes, exactly, integers don't have +-0 and +-infinity... only
(obviously) a kind of nan.

It's just that with the stuff I do I know I have some logical problem
in my formulas when I get any special floating point value anywhere,
and using --excess-precision can only make the numbers more precise.

Said differently: I don't know a thing about floats or numerics.

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