On Sat, 27 Aug 2011, Sönke Hahn wrote:
Hi!
I was reading through the Typeclassopedia ([1]) and I was wondering which type could be an instance of Pointed, but not of Applicative. But I can't think of one. Any ideas?
(Identity :+: Store s) is a comonad that is also instance of Pointed, but I do not believe it is an instance Applicative. newtype SemiStore s a = (Identity :+: Store s) a instance Pointed (SemiStore s) where pure a = Inl (Identity a) Coalgebras of the (Identity :+: Store s) comonad form the type of partial lenses so this isn't just an academic functor. -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.''