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.