ANNOUNCE: countable-0.1

[Maciej Piechotka]

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 
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