[Haskell-cafe] 1/0

David Roundy droundy at darcs.net
Mon Jun 16 20:31:22 EDT 2008

On Mon, Jun 16, 2008 at 05:08:36PM -0700, Don Stewart wrote:
> droundy:
> > On Mon, Jun 16, 2008 at 04:50:05PM -0700, John Meacham wrote:
> > > On Mon, Jun 16, 2008 at 04:41:23PM -0700, Evan Laforge wrote:
> > > > But what about that NaN->Integer conversion thing?
> > > 
> > > I think that may be a bug or at least a misfeature. The standard is
> > > somewhat vauge on a lot of issues dealing with floating point since
> > > it is such a tricky subject and depends a lot on the environment. The
> > > various rounding funcitons are particularly ugly IMHO. I added varients
> > > of them that preserved the floating point type and properly implemented
> > > IEEE behavior for jhc.
> > 
> > I think the Data.Binary guys think it's a feature, since they rely in
> > this behavior (well, they rely on the equivalently-foolish behavior of
> > toRational).  I think it's a bug.
> You mean:
>     instance Binary Double where
>         put d = put (decodeFloat d)
>         get   = liftM2 encodeFloat get get
> ?
> if you've a portable Double decoding that works in GHC and Hugs, I'm
> accepting patches.

I really don't understand why being portable is such an issue.  Is it
really better to behave wrong on every platform rather than behaving
wrong on a very small minority of platforms?

Anyhow, I've not hacked on binary, because I've not used it, and have
trouble seeing when I would use it.  So maybe I shouldn't have brought
the subject up, except that this use of decodeFloat/encodeFloat is a
particularly egregious misuse of floating point numbers.  decodeFloat
really ought to be a partial function, and this should be a crashing
bug, if the standard libraries were better-written.


More information about the Haskell-Cafe mailing list