[Haskell-cafe] profunctorial vs vanlaarhoven lenses
tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk
Wed May 2 16:10:12 UTC 2018
On Wed, May 02, 2018 at 03:07:05PM +0200, Paolino wrote:
> I'm trying to write a lens for a datatype which seems easy in the Twan van
> Laarhoven encoding but I cannot find it as easy in the profunctorial one
> data Q5 a b = Q51 a (Identity b) | Q52 [b]
> lq5Twan :: Applicative f => (b -> f b') -> Q5 a b -> f (Q5 a b')
> lq5Twan f (Q51 a bs) = Q51 a <$> traverse f bs
> lq5Twan f (Q52 bs) = Q52 <$> traverse f bs
> lq5Profunctor :: forall p a b b' . Traversing p => p b b' -> p (Q5 a
> b) (Q5 a b')
> Which simpler ways to write the lq5Profunctor we have ?
Is `wander lq5Twan` good enough, or is your question more philosophical?
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