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
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