Re: Option as applicative functor

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You could say that about an enormous number of traits.

There is a "growing movement" of people who delay introduction of the
unit operation, so you'd have a trait with ap+fmap instead (semigroups
instead of monoids).

On 06/08/11 23:03, Marius Danciu wrote:
> Right, but I guess here could have been an Applicative[T[_]] trait that
> those type constructors such as Option would mixin with, avoiding copy-paste
> in many cases. Applicative would probably have to extend Functor[T[_]] for
> having unit and fmap.
>
> Thanks,
> Marius
>
> On Sat, Aug 6, 2011 at 3:54 PM, Tony Morris <tonymorris@gmail.com> wrote:
>
> Well then that would require such a method on many type constructors,
> and the body of these methods would be a copy/paste show.
>
> def <*>[B](f: F[A => B]): F[B] = for { ff <- f; aa <- this } yield ff(aa)
>
>
> On 06/08/11 22:52, Marius Danciu wrote:
>>>> Precisely.
>>>>
>>>> Marius
>>>>
>>>> On Sat, Aug 6, 2011 at 3:35 PM, Tony Morris <tonymorris@gmail.com>
> wrote:
>>>>
>>>> On 06/08/11 21:27, Marius Danciu wrote:
>>>>>>> Hello,
>>>>>>>
>>>>>>> Is there a good reason why Scala Option is not an applicative functor
> ? I
>>>>>>> guess one could seamlessly convert an Option[T] to an Applicative[T]
>>>>  using
>>>>>>> implicits but still ..
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Marius
>>>>>>>
>>>>
>>>> Which Applicative do you mean? For the one in scalaz, there is an
>>>> implementation for Option.
>>>>
>>>> Do you want a method on Option[T] taking an Option[T => U], returning
>>>> Option[U]?
>>>>
>>>>
>>>>>
>
>>

- --
Tony Morris
http://tmorris.net/

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