Re: Filter on future doesn't make sense

Hi Avi,

I see what you mean.

I'd want to avoid discussing expectation since it is subjective. I will
however note that the actualnsemantics of the filter method on Future needs
improvement:
http://www.scala-lang.org/api/2.11.8/index.html#scala.concurrent.Future@filter(p:T=
>Boolean)(implicitexecutor:scala.concurrent.ExecutionContext):scala.concurrent.Future[T]

As for might not return the value, the same goes for all filter-methods:

List returns List, but it might not have any elements at all. Option
returns Option but can be Some or None, Future is either Success or Failure.

If success has an optionality aspect in your usage, use Future of Option to
express that, that would be my recommendation.

-- 
Cheers,
√
On Jul 1, 2016 9:20 AM, "Avi Levi" <[email protected]> wrote:

> Thanks Victor,
> Of course it can be implemented as you suggested. But still I can argue
> that the current implementation is not "really filtering" the results as
> one might expect and less expressive if it might or not return the value
> than Option is more expressive, don't you agree?
> On Jul 1, 2016 10:06 AM, "Viktor Klang" <[email protected]> wrote:
>
>> Hi Avi,
>>
>> Use Fututre[Option[Int]] if you want to deal with Some/None as a result
>> of filter ( f.map(_.filter(p) ) (alt. see monad transformers)
>>
>> --
>> Cheers,
>> √
>> On Jul 1, 2016 8:53 AM, "Avi Levi" <[email protected]> wrote:
>>
>> I was trying to figure out what should I accept when filtering over a
>> future .
>> the current implementation yields either a T or an exception which kind
>> of breaks referential transparency (doesn't it ?) .
>> on the other hand what can I expect given this expression
>>
>> *def foo(i:Int):Future[Int]*
>>
>> the type result of
>>
>> *foo(1).filter(_ % 2 == 0)*
>>
>>
>> I.M.H.O I would expect it to yield Option[T]  which makes more sense to
>> express that we might get a value that pass the filter or not . is that
>> make sense ?
>>
>> Cheers
>> Avi
>>
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