On Sat, 2 Feb 2008, Ben Butler-Cole wrote:
> [Resend with formatting maybe fixed.]
>
> Hello
>
> I'm trying to define functions that allow you to traverse a bounded
> enumeration, "wrapping" at the start and the end.
>
> My implementation looks like this:
>
> next, prev :: (Enum a, Bounded a) => a -> a
> next = turn 1
> prev = turn (-1)
>
> turn :: (Enum a, Bounded a) => Int -> a -> a
> turn n e = toEnum (add (fromEnum (maxBound::a) + 1) (fromEnum e) n)
> where
> add mod x y = (x + y + mod) `rem` mod
^^^
This should give warnings about a name clash with Prelude's 'mod'
function. Actually, I think you want to use 'mod' here instead of 'rem':
http://www.haskell.org/haskellwiki/Things_to_avoid#Forget_about_quot_and_rem
To fix the type of 'maxBound' a GHC extension is certainly overkill.
Better use `asTypeOf` instead.
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
