On Mon, 2010-09-06 at 03:54 -0700, Ashley Yakeley wrote:
countable: Countable, Searchable, Finite, Empty classes.
class Countable, for countable types class AtLeastOneCountable, for countable types that have at least one value class InfiniteCountable, for infinite countable types class Searchable, for types that can be searched over class Finite, for finite types class Empty, for empty types data Nothing, an empty type
Also includes these orphan instances:
instance (Searchable a,Eq b) => Eq (a -> b) instance (Finite a) => Foldable ((->) a) instance (Finite a) => Traversable ((->) a) instance (Show a,Finite a,Show b) => Show (a -> b)
It turns out Searchable includes some infinite types. Specifically, countable implements this:
instance (Countable c,Searchable s) => Searchable (c -> s)
using the algorithm described here:
http://math.andrej.com/2007/09/28/seemingly-impossible-functional-programs/
I would welcome improvements.
http://hackage.haskell.org/package/countable-0.1 cabal install countable darcs get http://code.haskell.org/countable/
See also this thread: http://thread.gmane.org/gmane.comp.lang.haskell.cafe/73275
Hmm. 1. Code formatting is very C#-like. At least for me it is hard to read the code that way (it IS matter of preference however) 2. countMaybeNext seems to need documentation. If I understand it correctly: countMaybeNext Nothing = 'minimalValue' countMaybeNext (Just x) = x + 1 Wouldn't be split it to: countNext :: a -> Maybe a initial :: Maybe a 3. Regards