Re: [Caml-list] What is an applicative functor?

[Alain Frisch <alain.frisch@lexifi.com>]

On 04/08/2011 08:50 AM, Andreas Rossberg wrote:
> Nitpick: the Make functor is still applicative. All functors in OCaml
> are applicative.

Nitpick²: except if you compile with -no-app-funct.

> Aside: In general, you really want to have both: functors with impure
> bodies better be generative, while functors with pure bodies should be
> applicative.

I'm not sure the benefits of applicative functors are worth the extra 
complexity they induce, especially if you want to support applicative 
functors in the same system as well. As far as I understand, applicative 
functors are useful primarily to give precise types to higher-order 
functors (which are rare enough).

It would be interested to see how much effort would be needed to adapt 
large code bases to compile with -no-app-funct (it probably amounts to 
giving a name to the result of a few functor applications).



Alain