Re: Filter on future doesn't make sense
Viktor Klang <[email protected]> Fri, 1 Jul 2016 11:30:51 +0200
| Newsgroups | gmane.comp.lang.scala |
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| Message-ID | <CANPzfU_DcRpCPzgR2-qXk36b_ia6LDjMXLGm_d4NE_ZK2cDDpw@mail.gmail.com> |
--001a113cf70677ca3405368fa446 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable But you don't get an exception on the success path. All operations on the success path will be skipped, just as for Option. --=20 Cheers, =E2=88=9A On Jul 1, 2016 10:35 AM, "Avi Levi" <[email protected]> wrote: > Hi Victor , > I totally agree that expectations are subjective . > But like you said a filter on List will return a List if no element compl= y > than we will get Nil which represents an empty container (empty list) > a filter on option will return a option if the element doesn't comply tha= n > we will get None which represents an empty container > following the same logic a filter on future should return something that > express empty container , defiantly not an exception, because it is not a= n > exception we do intend to filter those elements. > > > > 2016-07-01 10:50 GMT+03:00 Viktor Klang <[email protected]>: > >> 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 ne= eds >> improvement: >> http://www.scala-lang.org/api/2.11.8/index.html#scala.concurrent.Future@= filter(p:T=3D >> >Boolean)(implicitexecutor:scala.concurrent.ExecutionContext):scala.conc= urrent.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 Fail= ure. >> >> If success has an optionality aspect in your usage, use Future of Option >> to express that, that would be my recommendation. >> >> -- >> Cheers, >> =E2=88=9A >> 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 a= s >>> one might expect and less expressive if it might or not return the valu= e >>> 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 resul= t >>>> of filter ( f.map(_.filter(p) ) (alt. see monad transformers) >>>> >>>> -- >>>> Cheers, >>>> =E2=88=9A >>>> 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 kin= d >>>> 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 =3D=3D 0)* >>>> >>>> >>>> I.M.H.O I would expect it to yield Option[T] which makes more sense t= o >>>> express that we might get a value that pass the filter or not . is tha= t >>>> make sense ? >>>> >>>> Cheers >>>> Avi >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "scala-language" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> -- >>>> You received this message because you are subscribed to a topic in the >>>> Google Groups "scala-language" group. >>>> To unsubscribe from this topic, visit >>>> https://groups.google.com/d/topic/scala-language/wpGOB8f7qmY/unsubscri= be >>>> . >>>> To unsubscribe from this group and all its topics, send an email to >>>> [email protected]. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "scala-language" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "scala-language" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/scala-language/wpGOB8f7qmY/unsubscribe= . >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Sincerely, > Avi Levi > m: +972-52-3459959 > <https://www.linkedin.com/in/leviavi> > https://about.me/avi.levi > > -- > You received this message because you are subscribed to the Google Groups > "scala-language" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > --=20 You received this message because you are subscribed to the Google Groups "= scala-language" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to [email protected]. For more options, visit https://groups.google.com/d/optout. --001a113cf70677ca3405368fa446 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <p dir=3D"ltr">But you don't get an exception on the success path. All = operations on the success path will be skipped, just as for Option.</p> <p dir=3D"ltr">-- <br> Cheers,<br> =E2=88=9A</p> <div class=3D"gmail_quote">On Jul 1, 2016 10:35 AM, "Avi Levi" &l= t;<a href=3D"mailto:[email protected]">[email protected]</a>> wrote:<br ty= pe=3D"attribution"><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 = .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"rtl"><div dir= =3D"ltr">Hi Victor ,</div><div dir=3D"ltr">I totally agree that expectation= s are subjective .</div><div dir=3D"ltr">But like you said a filter on List= will return a List if no element comply than we will get Nil which represe= nts an empty container (empty list)</div><div dir=3D"ltr">a filter on optio= n will return a option if the element doesn't comply than we will get N= one which represents an empty container=C2=A0</div><div dir=3D"ltr">followi= ng the same logic a filter on future should return something that express e= mpty container , defiantly not an exception, because it is not an exception= we do intend to filter those elements.</div><div dir=3D"ltr"><br></div><di= v dir=3D"ltr">=C2=A0</div></div><div class=3D"gmail_extra"><br><div class= =3D"gmail_quote"><div dir=3D"ltr">2016-07-01 10:50 GMT+03:00 Viktor Klang <= span dir=3D"ltr"><<a href=3D"mailto:[email protected]" target=3D"_b= lank">[email protected]</a>></span>:</div><blockquote class=3D"gmai= l_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left= :1ex"><p dir=3D"ltr">Hi Avi,</p> <p dir=3D"ltr">I see what you mean.</p> <p dir=3D"ltr">I'd want to avoid discussing expectation since it is sub= jective. I will however note that the actualnsemantics of the filter method= on Future needs improvement: <a href=3D"http://www.scala-lang.org/api/2.11= .8/index.html#scala.concurrent.Future@filter(p:T=3D" target=3D"_blank">http= ://www.scala-lang.org/api/2.11.8/index.html#scala.concurrent.Future@filter(= p:T=3D</a>>Boolean)(implicitexecutor:scala.concurrent.ExecutionContext):= scala.concurrent.Future[T]</p> <p dir=3D"ltr">As for might not return the value, the same goes for all fil= ter-methods:</p> <p dir=3D"ltr">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 o= r Failure.</p> <p dir=3D"ltr">If success has an optionality aspect in your usage, use Futu= re of Option to express that, that would be my recommendation. </p><span><f= ont color=3D"#888888"> <p dir=3D"ltr">-- <br> Cheers,<br> =E2=88=9A</p></font></span><div><div> <div class=3D"gmail_quote">On Jul 1, 2016 9:20 AM, "Avi Levi" <= ;<a href=3D"mailto:[email protected]" target=3D"_blank">[email protected]</a>= > wrote:<br type=3D"attribution"><blockquote class=3D"gmail_quote" style= =3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir= =3D"ltr">Thanks Victor,<br> Of course it can be implemented as you suggested. But still I can argue th= at the current implementation is not "really filtering" the resul= ts as one might expect and less expressive if it might or not return the va= lue than Option is more expressive, don't you agree? </p> <div class=3D"gmail_quote">On Jul 1, 2016 10:06 AM, "Viktor Klang"= ; <<a href=3D"mailto:[email protected]" target=3D"_blank">viktor.kl= [email protected]</a>> wrote:<br type=3D"attribution"><blockquote class=3D"g= mail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-l= eft:1ex"><p dir=3D"ltr">Hi Avi,</p> <p dir=3D"ltr">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)</= p> <p dir=3D"ltr">-- <br> Cheers,<br> =E2=88=9A</p> <div class=3D"gmail_quote">On Jul 1, 2016 8:53 AM, "Avi Levi" <= ;<a href=3D"mailto:[email protected]" target=3D"_blank">[email protected]</a>= > wrote:<br type=3D"attribution"><blockquote style=3D"margin:0 0 0 .8ex;= border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">I was trying = to figure out what should I accept when filtering over a future .<div>the c= urrent implementation yields either a T or an exception which kind of break= s referential transparency (doesn't it ?) .</div><div>on the other hand= what can I expect given this expression=C2=A0</div><div> <p><span><i>def foo(i:Int):Future[Int]</i></span></p><p><span>the type resu= lt of=C2=A0</span></p><p><i>foo(1).filter(_ % 2 =3D=3D 0)</i></p> <p><span><br></span></p></div><div>I.M.H.O I would expect it to yield Optio= n[T] =C2=A0which makes more sense to express that we might get a value that= pass the filter or not . is that make sense ?</div><div><br></div><div>Che= ers</div><font color=3D"#888888"><div>Avi=C2=A0</div></font></div><font col= or=3D"#888888"> <p></p> -- <br> You received this message because you are subscribed to the Google Groups &= quot;scala-language" group.<br> To unsubscribe from this group and stop receiving emails from it, send an e= mail to <a href=3D"mailto:[email protected]" targ= et=3D"_blank">[email protected]</a>.<br> For more options, visit <a href=3D"https://groups.google.com/d/optout" targ= et=3D"_blank">https://groups.google.com/d/optout</a>.<br> </font></blockquote></div> <p></p> -- <br> You received this message because you are subscribed to a topic in the Goog= le Groups "scala-language" group.<br> To unsubscribe from this topic, visit <a href=3D"https://groups.google.com/= d/topic/scala-language/wpGOB8f7qmY/unsubscribe" target=3D"_blank">https://g= roups.google.com/d/topic/scala-language/wpGOB8f7qmY/unsubscribe</a>.<br> To unsubscribe from this group and all its topics, send an email to <a href= =3D"mailto:[email protected]" target=3D"_blank">s= [email protected]</a>.<br> For more options, visit <a href=3D"https://groups.google.com/d/optout" targ= et=3D"_blank">https://groups.google.com/d/optout</a>.<br> </blockquote></div> <p></p> -- <br> You received this message because you are subscribed to the Google Groups &= quot;scala-language" group.<br> To unsubscribe from this group and stop receiving emails from it, send an e= mail to <a href=3D"mailto:[email protected]" targ= et=3D"_blank">[email protected]</a>.<br> For more options, visit <a href=3D"https://groups.google.com/d/optout" targ= et=3D"_blank">https://groups.google.com/d/optout</a>.<br> </blockquote></div> <p></p> -- <br> You received this message because you are subscribed to a topic in the Goog= le Groups "scala-language" group.<br> To unsubscribe from this topic, visit <a href=3D"https://groups.google.com/= d/topic/scala-language/wpGOB8f7qmY/unsubscribe" target=3D"_blank">https://g= roups.google.com/d/topic/scala-language/wpGOB8f7qmY/unsubscribe</a>.<br> To unsubscribe from this group and all its topics, send an email to <a href= =3D"mailto:[email protected]" target=3D"_blank">s= [email protected]</a>.<br> For more options, visit <a href=3D"https://groups.google.com/d/optout" targ= et=3D"_blank">https://groups.google.com/d/optout</a>.<br> </div></div></blockquote></div><br><br clear=3D"all"><div><br></div>-- <br>= <div data-smartmail=3D"gmail_signature"><div dir=3D"rtl"><div><div dir=3D"r= tl"><div><div dir=3D"rtl"><div dir=3D"ltr"><span style=3D"color:rgb(51,51,5= 1);font-family:proxima-nova-1,proxima-nova-2,Tahoma,Helvetica,Verdana,sans-= serif;font-size:14px;line-height:21px">Sincerely,</span><br style=3D"color:= rgb(51,51,51);font-family:proxima-nova-1,proxima-nova-2,Tahoma,Helvetica,Ve= rdana,sans-serif;font-size:14px;line-height:21px"><span style=3D"color:rgb(= 51,51,51);font-family:proxima-nova-1,proxima-nova-2,Tahoma,Helvetica,Verdan= a,sans-serif;font-size:14px;line-height:21px">Avi Levi</span></div><div dir= =3D"ltr"><span style=3D"color:rgb(51,51,51);font-family:proxima-nova-1,prox= ima-nova-2,Tahoma,Helvetica,Verdana,sans-serif;font-size:14px;line-height:2= 1px">m: <a href=3D"tel:%2B972-52-3459959" value=3D"+972523459959" target=3D= "_blank">+972-52-3459959</a></span><span style=3D"color:rgb(51,51,51);font-= family:proxima-nova-1,proxima-nova-2,Tahoma,Helvetica,Verdana,sans-serif;fo= nt-size:14px;line-height:21px"><br></span></div><div dir=3D"ltr"><span styl= e=3D"color:rgb(51,51,51);font-family:proxima-nova-1,proxima-nova-2,Tahoma,H= elvetica,Verdana,sans-serif;font-size:14px;line-height:21px"><a href=3D"htt= ps://www.linkedin.com/in/leviavi" target=3D"_blank"><img src=3D"https://doc= s.google.com/uc?export=3Ddownload&id=3D0B82ayL0XJaZ5WEY0c2xWQWYxNDQ&= ;revid=3D0B82ayL0XJaZ5YklVWjUvcG9tQmNrVEFRSDhNd0lNLzUwKzlvPQ"><span></span>= <span></span></a></span></div><div dir=3D"ltr"><span style=3D"margin:0px;pa= dding:0px;border:0px;outline:0px;font-size:14px;font-family:proxima-nova-1,= proxima-nova-2,Tahoma,Helvetica,Verdana,sans-serif;vertical-align:baseline;= color:rgb(43,130,173);line-height:21px"><a href=3D"https://about.me/avi.lev= i" target=3D"_blank">https://about.me/avi.levi</a></span><br></div></div></= div></div></div></div></div> </div> <p></p> -- <br> You received this message because you are subscribed to the Google Groups &= quot;scala-language" group.<br> To unsubscribe from this group and stop receiving emails from it, send an e= mail to <a href=3D"mailto:[email protected]" targ= et=3D"_blank">[email protected]</a>.<br> For more options, visit <a href=3D"https://groups.google.com/d/optout" targ= et=3D"_blank">https://groups.google.com/d/optout</a>.<br> </blockquote></div> <p></p> -- <br /> You received this message because you are subscribed to the Google Groups &= quot;scala-language" group.<br /> To unsubscribe from this group and stop receiving emails from it, send an e= mail to <a href=3D"mailto:[email protected]">scal= [email protected]</a>.<br /> For more options, visit <a href=3D"https://groups.google.com/d/optout">http= s://groups.google.com/d/optout</a>.<br /> --001a113cf70677ca3405368fa446--