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  • 09:59
    lrytz commented #9388
  • 09:59
    lrytz assigned #9388
  • 09:38
    lrytz commented #9258
  • 09:34

    lrytz on 2.13.x

    Deprecate calling a type `?` wi… Merge pull request #9626 from s… (compare)

  • 09:34
    lrytz closed #9626
  • 09:26

    lrytz on 2.13.x

    enable fatal warnings in manual… Merge pull request #9627 from S… (compare)

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    lrytz closed #9627
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    RafalSumislawski commented #9625
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    lrytz commented #8365
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    RafalSumislawski commented #9625
Rob Norris
@tpolecat
E is in contravariant position in the return type so that might make sense.
moritz bust
@busti

How is it inferred

Maybe that was the wrong term

BTW shouldn't that be <: ?

Thats what I am was thinking too, but the compiler says something else.

Ryan Williams
@ryan-williams

cross-posting from shapeless room since i think it's a more general scala question:

i want to make a typeclass that only exists for type-constructors of nested-Seqs, e.g. Id, Seq, λ[A => Seq[Seq[A]]], etc.

import shapeless.{ Lazy, the }
sealed trait IsSeqs[R[_]]
object IsSeqs {
  implicit val id: IsSeqs[Id] = ???
  implicit def rec[R[T]](implicit r: Lazy[IsSeqs[R]]): IsSeqs[λ[ASeq[R[A]]]] = ???
}
the[IsSeqs[Id]]  // compiles
IsSeqs.rec[Id]   // compiles
the[IsSeqs[Seq]]  // could not find implicit value for parameter t: IsSeqs[Seq]
the[IsSeqs[λ[ASeq[Id[A]]]]]  // could not find implicit value for parameter t: IsSeqs[[A]Seq[A]]

any ideas why the last two lines don't compile?

afaict it seems like typeclass-derivation just doesn't "work" in the presence of type-lambdas…

sken
@sken77
wrote an implementation for Schnorr Signatures on the secp256k1 in scala using cats/scodec
this is the first working version. so i still need to work on a couple of things like improve the types of the primitives and add more tests
if any want to check it out and leave comments/review please open an issue ticket :)
arunsumbria
@arunsumbria
hi i am new to spark, i installed spark on windows 10 , when using below command its showing path dosent exist, i have winutils too under c drive
 val df = spark.read.csv("file:///C:/spark/myprog/emp")
org.apache.spark.sql.AnalysisException: Path does not exist: file:/C:/spark/myprog/emp;
i have provided 777 permission to c:\tmp\hive
vijendra singh
@viju0731_twitter
How do i call object from parent class to child class
?
aby idea. i know how to call methods but when i am trying same way for object objectname extends
it is not working for me
Rob Norris
@tpolecat
can you create a minimal example that demonstrates what you're trying to do?
Dominic Egger
@GrafBlutwurst
Hi everyone. So I have a REST API that guarantees idempotence and I want to do a local trivial fixed size cache. what's the smartest way to keep this RT? State?
Fabio Labella
@SystemFw
@GrafBlutwurst Ref + IO
possibly behind a final tagless api to not expose implementation details
State can't deal with concurrent state, so you can't do (most types of) caching with it
Dominic Egger
@GrafBlutwurst
yeah that's what I'm doing anyway I don't want to expose the caching to external user except size
ah I see
<3 looks exactly like what I needed thanks!
Fabio Labella
@SystemFw
let me know if you're having problems encoding the logic you need there, but generally fs2.Ref + fs2.Promise (now cats.effect.Ref and cats.effect.Deferred) are your friends
moritz bust
@busti
Is there a way to automatically create a companion object for a class?
ndv87
@ndv87
@Busti in IDEA u can Alt+Insert -> Comp obj
moritz bust
@busti
That is a nice idea, but I am thinking more about a code thing here...
What I am trying to do is to implicitly create a companion object for every child of a class. Since it always has the same members, there is no need to re-write it every time that class is extended.
But I guess that could only be solved by codegen, which might not be that good of an idea.
Dominic Egger
@GrafBlutwurst
@SystemFw this does this seem sensible?
I'll only have to do a fixed size alternative to Map and evict LRU style when adding
maybe just use Chris' scalacache
Fabio Labella
@SystemFw
@GrafBlutwurst there's a problem with that
you are creating new Ref and HttpClient every time
with the Client, it's just wasteful
with the Ref, it won't work because you aren't sharing the state
Dominic Egger
@GrafBlutwurst
lazyness?
Fabio Labella
@SystemFw
nope, purity
if you mention cache, you create a new cache
Dominic Egger
@GrafBlutwurst
oh right. substitution ... derp
Fabio Labella
@SystemFw
if you want to share the state, you need to pass it as an argument and flatMap everytime
this is a feature because it means that the region of state sharing is the same as your call graph
but you need to get used to it
in caching terms, caches always reduce to having type IO[IO[A]], and not IO[A]
Dominic Egger
@GrafBlutwurst
so i necessarily need to expose my state outside?
Fabio Labella
@SystemFw

in this case if you have

trait Cache[F[_], A] {
   def get: F[A]
}

then the constructor needs to be

object Cache {
  def create: F[Cache[F, A]] = ....
no, you don't have to expose the state, but you will have F[Cache[F,
and for that the same argument applies, you need to pass the cache wherever it's needed, and then create it and flatMap it once at the end of the region of sharing you want to create, e.g. main if your whole app needs it
you can always unsafeRunSync it if you want a truly global one but I'd discourage that
I'd rather be in full control of who shares what state
Vasco Dias
@vascorsd
Hi, is there other ways to define the jvm flags required for scala to compile when using sbt (specifically the Xss)? I' using the $JVM_OPTS environment var. I see it could be maybe also on $SBT_OPTS or any of the opts files that sbt also runs. I'm wondering because I have a colleague saying it should go inside the build.sbt file directly and stay defined there... looking for a good reason and/or argument why it shouldn't.