On 6 September 2010 00:11, Sebastian Fischer
Just because we don't have a use now doesn't mean it might not be useful in the future.
I am suspicious about complicating a design for potential future benefits.
However, difference lists provide an example of a type that support Pointed more naturally than Applicative: the dlist package [1] provides Applicative and Monad instances but only by converting to normal lists in between.
Note that even fmap cannot be defined without converting difference lists to normal lists in between. The natural interface to difference lists would be Pointed (without a Functor superclass) and Monoid.
Hmmm.... is there any reason for Functor to be a superclass of Pointed? I understand Functor and Pointed being superclasses of Applicative (which in turn is a superclass of Monad), but can't see any relation between Pointed and Functor... -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com