Hi Bringing up an old thread, but this issue just bit me in real life:
[0, 2.5 .. 3.75 ] = [0, 2.5, 5.0] I was comparative testing some C++ and some Haskell, and its a shame when its the Haskell that is clearly wrong! I don't think any end decision was reached in this thread, but I think this is sufficiently incorrect to call the Haskell 98 behaviour a bug. Thanks Neil On Wed, Oct 22, 2008 at 10:11 AM, Simon Marlow <[EMAIL PROTECTED]> wrote: > Malcolm Wallace wrote: > >> Phil proposes that, although retaining the instances of Enum for Float >> and Double, we simplify the definitions of the numericEnumFrom family: >> >> numericEnumFromThenTo :: (Fractional a, Ord a) => a -> a -> a -> [a] >> numericEnumFrom = iterate (+1) >> numericEnumFromThen n m = iterate (+(m-n)) n >> numericEnumFromTo n m = takeWhile (<= m) (numericEnumFrom n) >> numericEnumFromThenTo n m p = takeWhile (<= p) (numericEnumFromThen n m) > > I'll leave it to the floating-point experts to decide exactly what to do > here for Haskell' (but I note that David Roundy's version looks better than > the iterate version above, because the errors won't accumulate). > >> But as maintainer and bug-fixer of the Haskell'98 Report, I have also >> been asked whether we should make this change retrospectively to the >> Haskell'98 language (as a "typo"). Since it involves not merely an >> ordinary library function, but a Prelude function, and moreover a >> function that is used in the desugaring of syntax, it is less clear to >> me whether to alter Haskell'98. > > We definitely can't make breaking changes to Haskell 98; this would be much > more than a "typo". > > However, this does give us a problem if we decide to make a change here for > H', as Neil points out, because there would be two mutually-incompatible > instances for Enum Float. We'd need to have a clear distinction between > programs that are Haskell 98 and those that are not, with only the former > allowed to use the haskell98 package. > > Cheers, > Simon > > _______________________________________________ > Haskell-prime mailing list > Haskell-prime@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-prime > _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime