Functor => Pointed => Applicative => Monad

Conor McBride conor at
Wed Dec 1 14:04:30 CET 2010

On 1 Dec 2010, at 10:44, John Lato wrote:

> On Wed, Dec 1, 2010 at 12:17 AM, Conor McBride <conor at 
> > wrote:
> On 30 Nov 2010, at 16:05, David Menendez wrote:
> I contend that there is little benefit to splitting Applicative. By
> itself, 'pure' is simply too loosely defined.
> It would be more interesting to have a type class for those
> functors which were not pointed. Relatively speaking.
> I'm completely lost now.  Do you mean something other  than  
> Functor?  What do you have in mind?

I was being slightly facetious. I was also wondering what
value the Pointed class would add, by asking which instances
of Functor would fail to be Pointed. The constantly Zero
(or Void, if you insist) Functor? What else? I suggest that
failure to be Pointed is a more curious and interesting
property of a Functor than being Pointed, but I don't quite
see a compelling case for either situation having a class to

Sorry to be oblique


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