Pointed [Re: 2014 Applicative => Monad proposal]

[Anthony Cowley]

On 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

I hit exactly this need somewhat regularly. There was some discussion about it on IRC recently, and the consensus was that there isn't anything quite right for this purpose in any commonly used package. 

Anthony




> 
> 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/
> 
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