[Haskell] Re: Platform-dependent behaviour with functions on NaN

David Roundy droundy at darcs.net
Fri Apr 14 06:34:31 EDT 2006

On Thu, Apr 13, 2006 at 04:24:45PM +0100, Simon Marlow wrote:
> >- get an implementation of this in GHC which computes the same results 
> >for all platforms?
> I would certainly hope so, if we can find the source of the discrepancy 
> and devise a fix.

I'd just point out that C compilers don't allow you to get the same results
on all platforms, and doing so in general requires slow floating point
arithmetic, mostly because there don't seem to be any platforms in
production that implement IEEE arithmetic.  I wouldn't like the standard
(or compiler) to enforce special checks every time we do floating point
arithmetic.  It would be nice, perhaps, as an option, but that would (as I
understand it) be considerable effort and a considerable slowdown, for
relatively little benefit, which is why gcc hasn't bothered with it
either.  I imagine that if producing reproducible arithmetic is beyond the
means of the gcc development team, it's also beyond that of the ghc
development team, especially since you can always get reproducible
arithmetic (I presume) by using Rationals.
David Roundy

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