Well, I've suggested it: https://github.com/scala/scala/pull/5137
On Wednesday, April 27, 2016 at 4:41:07 PM UTC+2, Bruno Bieth wrote:
>
> I agree with Roland that having a Future[Unit] may lead to subtle bugs due
> to the value discarding mechanism. My favorite is mixing map and flatMap by
> mistake:
>
> // this compiles just fine: map[T] is infered to be map[Unit], then Future
> { println("two"); Done } which is of type Future[Done] is discarded to
> satisfy map[Unit]
> def compute: Future[Unit] = Future[Done] { println("one"); Done }.map( _
> => Future { println("two"); Done } )
>
> On the other hand:
>
> // won't compile!
> def compute: Future[Done] = Future[Done] { println("one"); Done }.map( _
> => Future { println("two"); Done } )
>
> Now, this could be a good reason for bringing this into the scala library?
>
> Bruno
>
>
> On Wednesday, February 24, 2016 at 5:12:24 PM UTC+1, rkuhn wrote:
>>
>> There is one other use that these types can be put to: Scala’s habit of
>> conjuring a Unit out of thin air where needed can make it non-obvious where
>> all the exit points of a method are. Declaring a different return type
>> means that all such points need to be marked out explicitly. But outside
>> the method this is not very useful (and this was also not the reason for
>> the introduction of these types). As Patrik and Konrad note these are
>> intended to be used a type parameters.
>>
>> Regards,
>>
>> Roland
>>
>> 24 feb 2016 kl. 15:36 skrev Konrad Malawski <kt...@lightbend.com>:
>>
>> Yeah, agree with Patrik here.
>> It's mostly for `Future[Done]` and situations like that, void/Unit is
>> still fine in normal return values.
>>
>> --
>> Cheers,
>> Konrad 'ktoso’ Malawski
>> <http://akka.io/>Akka <http://akka.io/> @ Lightbend
>> <http://typesafe.com/>
>> <http://lightbend.com/>
>>
>> On 24 February 2016 at 13:35:02, Patrik Nordwall (patrik....@gmail.com)
>> wrote:
>>
>>
>>
>> On Wed, Feb 24, 2016 at 1:23 PM, rklaehn <rkl...@gmail.com> wrote:
>>
>>> Hi Konrad,
>>>
>>> So, if it wasn't for backward compatibility, the return type of tell
>>> would be akka.NotUsed, to signal that successful return does not tell you
>>> anything about successful processing of the message (akka.Done would
>>> certainly be wrong)?
>>>
>>
>> That would be to take it one step to far, I would say. Ordinary methods
>> should still be declared with void (java) or Unit (scala) return types.
>> Done and NotUsed are mostly interesting when the return value is not
>> immediate, such as in a CompletionStage (java), Future (scala), or stream
>> materialized value.
>>
>>
>> Cheers,
>>
>> Rüdiger
>>
>> On Wednesday, February 24, 2016 at 11:43:33 AM UTC+1, Konrad Malawski
>> wrote:
>> Hey Rüdiger,
>> yeah those can definitely be used in all kinds of APIs.
>> The reason we have them mostly in Streams for now is because we could not
>> break compatibility in akka-actor for example.
>>
>> The types are intended to be simply more informative than plain `Unit`,
>> so wherever that's needed feel free to use them :-)
>>
>> --
>> Cheers,
>> Konrad 'ktoso’ Malawski
>> <http://akka.io/>Akka <http://akka.io/> @ Lightbend
>> <http://typesafe.com/>
>> <http://lightbend.com/>
>>
>> On 24 February 2016 at 11:41:57, rklaehn (rkl...@gmail.com) wrote:
>>
>> Hi all,
>>
>> given the prominent position of akka.Done and akka.NotUsed: are these
>> only meant to be used within akka streams, or also elsewhere?
>>
>> I am currently trying to introduce futures into a codebase with a lot of
>> blocking, and it sure would be helpful to distinguish between methods
>> returning Unit where successful return signals successful completion, and
>> methods where successful return means nothing (e.g. because it is sending
>> to some actor inside the method using !).
>>
>> Would this be a valid use case for using Done and NotUsed?
>>
>> Cheers,
>>
>> Rüdiger
>> --
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>> --
>>
>> Patrik Nordwall
>> Lightbend <http://www.lightbend.com/> - Reactive apps on the JVM
>> Twitter: @patriknw
>>
>> [image: Lightbend] <http://www.lightbend.com/>
>> --
>> >>>>>>>>>> Read the docs: http://akka.io/docs/
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>> --
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>>
>>
>> *Dr. Roland Kuhn*
>> *Akka Tech Lead*
>> Typesafe <http://typesafe.com/> – Reactive apps on the JVM.
>> twitter: @rolandkuhn
>> <http://twitter.com/#!/rolandkuhn>
>>
>>
--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
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