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  • Jan 29 2019 12:10

    xuwei-k on 7.2.x

    fix compile error with latest S… (compare)

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Rui Gonçalves

Hi! I'm trying to migrate pureconfig to scalaz 7.3 (pureconfig/pureconfig#752) but I'm getting an error about a missing instance of Unapply:

<console>:42: error: Implicit not found: scalaz.Unapply[scalaz.Applicative, Unit]. Unable to unapply type `Unit` into a type constructor of kind `M[_]` that is classified by the type class `scalaz.Applicative`. Check that the type class is defined by compiling `implicitly[scalaz.Applicative[type constructor]]` and review the implicits in object Unapply, which only cover common type 'shapes.'
       List(validConf, invalidConf, anotherInvalidConf).traverseU { c =>

I couldn't find any migration guide or release notes for scalaz 7.3. Do I have to import something now?

Georgi Krastev
Have you tried enabling -Ypartial-unification and just using traverse? Those Unapply tricks shouldn't be necessary.
only if typeclass has a particular shape though
This message was deleted
def f[F[_]](implicit E: MonadError[F, String], implicit T: MonadTell[F, Vector[String]]) = ...
import scalaz._
import Scalaz._

type W[A] = Writer[Vector[String], A]
type T[A] = EitherT[W, String, A]

I get errors about not finding the implicits. Do I need to import something else? Is that type T making things tricky for the implicit resolution?
just needed partial unification on
also switched to cats monadchronicle drops mic
Emily Pillmore
Hey folks, if anyone is interested: https://twitter.com/pitopos/status/1265428158913839104
Buk Lau
can I just check - I should use this:
resolvers += Resolver.sonatypeRepo("snapshots")
libraryDependencies += "org.scalaz" %% "scalaz-base" % "1804fbf6-SNAPSHOT"
libraryDependencies += "org.scalaz" %% "scalaz-core" % "7.3.1"
if you want to use scalaz8 preview, yes
Buk Lau
what do you recommend for a new project?
I'm coming back to scalaz after a few years away so haven't been following anything closely
Buk Lau
also the discord invite is expired - can I get an new invite?
i would recommend the stable version
Buk Lau
cool, thanks @OlegYch
note that most folks use cats these days
Buk Lau
yeah, I've been using cats past 12 months
what's the roadmap for scalaz? is there one?
don't think so
Emily Pillmore
@mk9023_gitlab not that we've been tracking. The project doesn't really need much improvement, which is cool.
Stephen Compall
you all might be interested in the Scalaz Files series on my blog, which is up to four parts now https://failex.blogspot.com/
Justin Heyes-Jones
Buk Lau
why is IsoSet called IsoSet and not just Iso?
Tony Morris
The roadmap is to switch to using Haskell, and where Scala is a requirement, to implement a compiler using Haskell. Handwriting Scala is not recommended.
Antriksh Parmar
Hello All, where do I find an updated Scalaz documentation? Most of the documentations I have seen by far are out of date.
or just open your sbt project in intellij

Hi there.
We are currently in the progress of Updating scalaz from 7.2.30 to 7.3.2 but we are having a problem with our tests that are failing now (possibly due to The schange of Tree.flatten to EStream).
The test that is successful in 7.2.30 but not in 7.3.2 is a more complex version of:

import scalaz.Scalaz.ToTreeOps
import scalaz.Tree

val value1: Tree[String] = "hi".node("huhu".leaf, "haha".leaf)
val value2: Tree[String] = "hi".node("huhu".leaf, "haha".leaf)

value1.flatten == value2.flatten shouldBe true

Are we making something wrong? Or is there a better way to check if the trees contain the same elements?

Harrison Houghton
Does tt work with Eq instead? import scalaz.Scalaz._ and then use === iirc
@hrhino Yes the === syntax does work with this Tree[String] because there is an implicit EStream[String]
with the creation of the (in the real usecase) needed Order[A] we made it Work
Thank you very much for your Help
Hi everybody. I upgrade my scala from 2.11 to 2.12 and my scalaz from 7.1 to 7.2.30 and i have an issue with @@ type
I have this error when i try to json binding the type with play json
No instance of play.api.libs.json.Format is available for scalaz.TagModule.$at$at[scala.Double, domain.common.number.positivedouble.PositiveDoubleTag]
indeed i have this type
private[positivedouble] sealed trait PositiveDoubleTag
type PositiveDouble = Double @@ PositiveDoubleTag
Someone know what kind of issue is ?
Why A paremeter of NonEmptyList[A] is not covariant anymore ?
It is impossible to use it with ADT anymore no ?
@ubourdon did you implement Format[PositiveDouble] in object PositiveDoubleTag?
Stephen Compall
@ubourdon covariance is not a prerequisite of using anything with an ADT
@ubourdon you also need to point out what implicit you expect to resolve and where you defined it
Lalli Nuorteva

Hi, I'm trying to use https://github.com/scalaz/scalaz-deriving in my play 2.8.0 project. I've defined the class like this:

import play.api.libs.json
import scalaz.annotation.deriving
import io.estatico.newtype.macros._

@newtype final case class PurchaseId(value: String)

However when i'm compiling the project, i get an error like this:

Error:(8, 27) not found: value deriving
@newtype final case class PurchaseId(value: String)

Does anyone have an idea why could this happen?

Jozef Koval
Is there any simple way how to use Traverse#sequence with List[Try[A]]?
Jozef Koval
I ended up with List[Disjunction[Throwable, A]]
Emily Pillmore
I am rejoined
⛈ :ghost: muahahhaha :jack_o_lantern: 🗝
hrhino @hrhino sets mode +b emilypi
Emily Pillmore
u wot m8
Yang, Bo
Hi, anyone here is interested in the lawful ListT? I created a PR scalaz/scalaz#2334 . I would appreciate any feedback.
Andreas Joseph Krogh

Hi, I'm using Scala-2.12.15 and have problems getting ValidationNels to work with Applicative, this doesn't compile in 7.3 but compiles in 7.2:

import scalaz.Scalaz._
val foo = Some("Stuff").toSuccess("Missing stuff").toValidationNel
val bar = Option.empty[String].toSuccess("Missing other.").toValidationNel
foo ⊛ bar

How do I make this compile using 7.3?