Re: Pointed [Re: 2014 Applicative => Monad proposal]

Pointed is a superclass of Applicative, taking the role of pure, but not related to Functor. I do not see the problem. On 24.05.2013 19:59, Dan Doel wrote:

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 mailto: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 tel:24.05.2013%2017:28, Roman Cheplyaka wrote:

I completely agree with Edward here.

* Edward Kmett mailto: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 mailto:andreas.abel@ifi.lmu.de>__wrote:

+1 AMP +1 MINIMAL +1 Pointed in base

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

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-- 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/