On Mon, 16 Jun 2008, Dan Doel wrote:

On Monday 16 June 2008, Evan Laforge wrote:

...

(huge negative number)

Ok, so integral types don't have that exceptional value. Shouldn't trying to convert NaN or Infinity to an Integral throw something? Is it a performance thing? I'd think if you're converting to Integer you don't really need hardware level performance anyway, so a couple of checks wouldn't kill anyone.

This is a (known by some) bug of sorts in the various floating point -> integral transformations (which ultimately boil down to decodeFloat or something like that at some point). It apparently doesn't know about the various exceptional values in the IEEE representation, so it just treats the representation like any other value. Infinity and NaN look like various huge numbers if you interpret them like any other value, so that's what you get out of round/ceiling/floor/etc.

It's not ideal, but I guess no one's bothered to fix it. Might be something to bring up on the libraries mailing list.

This could be combined with improving performance: http://hackage.haskell.org/trac/ghc/ticket/2281 http://hackage.haskell.org/trac/ghc/ticket/2271 http://hackage.haskell.org/trac/ghc/ticket/1434