David Menendez wrote:
On Mon, Nov 29, 2010 at 11:26 AM, Isaac Dupree
Is it useful to have Pointed non-Functors?
Is Pointed useful at all? The last time this discussion came up, I asked for algorithms which were generic over pointed functors (in the same way that traverse is generic over applicative functors) and no one could think of any.
I remember that I have recently abused Applicative in connection with Traversable in order to get the 'pure' method. First example: A general implementation of a 'peek' for traversable structures: http://hackage.haskell.org/packages/archive/storable-record/0.0.2.3/doc/html... Second example: The liftPoint function in http://code.haskell.org/~thielema/streamed/src/Sound/MIDI/ALSA/Causal.hs that lifts a not-quite arrow (T a b) to a (T (t a) (t b)) where 't' is Traversable.