Functor => Pointed => Applicative => Monad

David Menendez dave at
Tue Nov 30 17:05:27 CET 2010

On Tue, Nov 30, 2010 at 5:31 AM, John Lato <jwlato at> wrote:
>> From: David Menendez <dave at>
>> Is Pointed useful at all? The last time this discussion came up, I
>> asked for algorithms which were generic over pointed functors (in the
>> same way that traverse is generic over applicative functors) and no
>> one could think of any.
> It's useful for 'singleton' on probabilistic data structures (e.g. a Bloom
> filter).

Again, I'm asking for clients, not implementations. Are there any
useful, non-trivial functions which are parameterized by arbitrary
Pointed functors?

Consider the way Happy is parameterized by a monad. Does anything
similar exist for Pointed?

I contend that there is little benefit to splitting Applicative. By
itself, 'pure' is simply too loosely defined.

Dave Menendez <dave at>

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