[Haskell-cafe] ANN: unfoldable-0.4.0

wren ng thornton wren at freegeek.org
Sat Apr 28 02:40:25 CEST 2012

On 4/26/12 3:52 PM, Roman Cheplyaka wrote:
> * Tillmann Rendel<rendel at informatik.uni-marburg.de>  [2012-04-26 21:34:21+0200]
>> Hi,
>> Sjoerd Visscher wrote:
>>> Just as there's a Foldable class, there should also be an Unfoldable class. This package provides one:
>>>    class Unfoldable t where
>>>      unfold :: Unfolder f =>   f a ->   f (t a)
>> Just to be sure: That's not a generalization of Data.List.unfoldr, or
>> is it somehow?
> It seems to be -- see
> https://github.com/sjoerdvisscher/unfoldable/blob/master/src/Data/Unfoldable.hs#L84
> (although that is much more complicated than Data.List.unfoldr)

I must admit I'm a bit weirded out by the (Bounded a, Enum a) 
restriction on the Either, tuple, and Constant instances. Why not just 
use Unfoldable a, or have a class specifically devoted to unfolding * types?

Live well,

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