Where is Pointed supposed to live in the hierarchy? For instance, someone mentioned Set. But Set is not eligible to have a Functor instance.

So do we just have Pointed type functions that aren't necessarily Functors? And if they are Functors/Applicatives/Monads they're supposed to behave nicely?

And if not, then several collections are excluded from being Pointed, and I'm not entirely sure which collections you're using. Just many different sequence types?

On Fri, May 24, 2013 at 1:02 PM, Andreas Abel <andreas.abel@ifi.lmu.de> wrote:

I do not use Pointed a lot, but a situation where it comes natural is when I want to emit elements into a collection f. Then I need

Pointed f -- to emit a single element
Monoid (f a) -- to join two collections

Using Applicative or Monad is overdoing it.

Maybe you have a better suggestion how to organize my task which I have not considered yet...

Cheers, Andreas

On 24.05.2013 17:28, Roman Cheplyaka wrote:

I completely agree with Edward here.

* Edward Kmett <ekmett@gmail.com> [2013-05-24 11:20:51-0400]

For the record I'm actually -1 on including Pointed.

My experience is that there are very few uses for the class that permit you
to reason about your code without one-off ad hoc reasoning based on the
particular instance you are given. Now, the Apply and Bind classes on the
other hand... =) Though, to be fair, I couldn't seriously propose including
either of those, either. Even I can't be bothered to instantiate them all
the time!

-Edward

On Fri, May 24, 2013 at 11:13 AM, Andreas Abel <andreas.abel@ifi.lmu.de>wrote:

+1 AMP
+1 MINIMAL
+1 Pointed in base

--
Andreas Abel <>< Du bist der geliebte Mensch.

Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY

andreas.abel@ifi.lmu.de
http://www2.tcs.ifi.lmu.de/~abel/

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