The problem is that is more than one way to compose two applicative functors! If one is a pointed functor and the other is a monad, then there are at least 3 different forms of distributive laws that might be used to compose them to obtain a monad (and as a side effect, obtain an applicative) in addition to the closure of applicative functors under composition. I would strongly advise against enshrining applicative/applicative composition directly in Control.Applicative. If you want to place it in something off to the side like Control.Applicative.Composition, then by all means. -Edward Kmett. On Wed, Jun 17, 2009 at 5:33 PM, Henning Thielemann < lemming@henning-thielemann.de> wrote:

In the TypeCompose package there is the O data type for composing two applicative functors

http://hackage.haskell.org/packages/archive/TypeCompose/0.6.4/doc/html/Contr...

However I hesitate to import this package because of a lot of needed type extensions. But since 'O' seems to be the canonical way for combining two functors, could we add it to Control.Applicative? _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries