On Fri, Sep 28, 2007 at 05:54:23PM +0100, Brian Hulley wrote:
> Yes this type should be fine. To implement reversor though you'd still need
> to first convert from the concrete list to whatever foldable you're using,
> before reversing the foldable, or implement something more general eg:
>
> reversor :: (Foldable f, Foldable g) :: f a -> g a
One cannot define such a function, as Foldable provides no way to build
things. However one can define
reversor :: Traversable f => f a -> f a
which returns something of the same shape, but with the contents reversed.
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