Well, I can accept it as an evidence of why not to use the profunctor encoding for multi target lens (if that's the name). But I guess we are already in philosophy (so I'm more puzzled than before) and I hope you can elaborate more. .p 2018-05-02 18:10 GMT+02:00 Tom Ellis < tom-lists-haskell-cafe-2013@jaguarpaw.co.uk>:
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? _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.