Pointed [Re: 2014 Applicative => Monad proposal]

[Dan Doel]

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 at 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 at 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 at 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 at ifi.lmu.de
> http://www2.tcs.ifi.lmu.de/~**abel/ <http://www2.tcs.ifi.lmu.de/~abel/>
>
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