[Haskell-cafe] diff implementation in haskell

[Victor Nazarov]

Are there pure haskell implementations of diff and diff3 algorithms. Like:

> data Diff a = Deleted [a] | Common [a] | Added [a]
>
> diff :: Eq a => [a] -> [a] -> [Diff a]
>
> diff3 :: Eq a => [a] -> [a] -> [a] -> [a]

or smth more general like:

> class Diff a where
>   type Difference a
>   diff :: a -> a -> Difference a
>   patch :: a -> Difference a -> a
>
> prop_diffpatch a b = patch a (diff a b) == b

?

If not, where can I start towards the implementation? What's the way
to do it more functionally?
--
Victor Nazarov