On Wed, Aug 22, 2007 at 06:36:15PM +0100, Neil Mitchell wrote: > Hi > > > If Num obeys ring axioms, fromInteger is a perfectly fine > > ring-homomorphism. (It's also the first or second homomorphism taught.) > > Does Int obey these axioms? I'm thinking that assuming properties > about things such as numbers is very likely to go wrong very quickly. > Monads you might be able to get away with, Numbers you probably can't.
Int does obey the axioms, it's the classical ring ℤ[4294967296]. Double, however, does not: [EMAIL PROTECTED]:~$ ghci GHCi, version 6.7.20070712: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> let x = 10000000000000000000000 ; y = 1 - x Prelude> fromInteger (x + y) :: Double 1.0 Prelude> fromInteger x + fromInteger y :: Double 0.0 Stefan
signature.asc
Description: Digital signature
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
