scalaz/scalaz

Scalaz: Functional programming for Scala | IRC: irc://irc.freenode.net/scalaz | Discord: https://discord.gg/eYZhcW | Channel logs http://ircbrowse.net/scalaz | Latest stable release: 7.2.26 | http://github.com/scalaz/scalaz | https://scalaz.github.io/scalaz/#scaladoc Wokest message of the day: Well, I personally think that he's solving the problem of typeclasses not being horrible in Scala - @oleg-py

Harrison Houghton

@hrhino

Practically speaking, you do so with a: A => pairs.find(_._1 == a)

Barry Zhong

@zhongdj

is scalaz still active?

Dimitar Georgiev

@dimitarg

@hrhino right, I got thrown off somehow. thanks for the patient explanation.
Finite a implies an equality notion, and surely allValues :: [a] is going to give me back all distinct values.
(I guess I was thinking about injectivity and confused it with function-ness. Flipped the arrows somehow)

@zhongdj this channel, not so much. What do you mean by "active"?

Philip Schwarz

@philip_schwarz_twitter

@zhongdj https://twitter.com/scalazlog

Jozef Koval

@jozi-k

Hi guys, i am struggling with:

val foo = List(Validation.failure("bar"), Validation.success(8), Validation.success(10))
foo.sequence

The error says

<console>:19: error: could not find implicit value for parameter ev: scalaz.Validation[String,Int] === G[B]

I am trying to get List[Int] or List[String] (depends on existence of Failure). My questions are:

What does the error says? (After some digging I think it should say there is no Traversable instance for Validation instead)
Is there any reasonable way to get the expected result?

Georgi Krastev

@joroKr21

It sounds like you need the -Ypartial-unification compiler option

Jozef Koval

@jozi-k

That did the trick @joroKr21 . Thanks a lot!

mmuhluri

@mmuhluri

Whenever I try to import package on sbt console I keep getting an error, What can be a problem?
scala> package com.packait.scala.book

<console>:1: error: illegal start of definition
package com.packait.scala.book
^

Rui Gonçalves

@ruippeixotog

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

@joroKr21

Have you tried enabling -Ypartial-unification and just using traverse? Those Unapply tricks shouldn't be necessary.

OlegYch

@OlegYch

only if typeclass has a particular shape though

jrciii

@jrciii

This message was deleted

jrciii

@jrciii

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]

f[T].run.run

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?

jrciii

@jrciii

just needed partial unification on

also switched to cats monadchronicle drops mic

Emily Pillmore

@emilypi

Hey folks, if anyone is interested: https://twitter.com/pitopos/status/1265428158913839104

Buk Lau

@mk9023_gitlab

can I just check - I should use this:

resolvers += Resolver.sonatypeRepo("snapshots")
libraryDependencies += "org.scalaz" %% "scalaz-base" % "1804fbf6-SNAPSHOT"

not

libraryDependencies += "org.scalaz" %% "scalaz-core" % "7.3.1"

OlegYch

@OlegYch

if you want to use scalaz8 preview, yes

Buk Lau

@mk9023_gitlab

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

@mk9023_gitlab

also the discord invite is expired - can I get an new invite?

OlegYch

@OlegYch

i would recommend the stable version

Buk Lau

@mk9023_gitlab

cool, thanks @OlegYch

OlegYch

@OlegYch

note that most folks use cats these days

Buk Lau

@mk9023_gitlab

yeah, I've been using cats past 12 months

what's the roadmap for scalaz? is there one?

OlegYch

@OlegYch

don't think so

Emily Pillmore

@emilypi

@mk9023_gitlab not that we've been tracking. The project doesn't really need much improvement, which is cool.

Stephen Compall

@S11001001

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

@justinhj

Nice!

Buk Lau

@mk9023_gitlab

why is IsoSet called IsoSet and not just Iso?

Tony Morris

@tonymorris_gitlab

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

@__Antriksh_twitter

Hello All, where do I find an updated Scalaz documentation? Most of the documentations I have seen by far are out of date.

OlegYch

@OlegYch

https://www.javadoc.io/doc/org.scalaz/scalaz_2.13/7.3.1/scalaz/index.html

or just open your sbt project in intellij

TjarkoG

@TjarkoG

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

@hrhino

Does tt work with Eq instead? import scalaz.Scalaz._ and then use === iirc

TjarkoG

@TjarkoG

@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

@ugobourdon

@ubourdon

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 ?

@ugobourdon

@ubourdon

Why A paremeter of NonEmptyList[A] is not covariant anymore ?

It is impossible to use it with ADT anymore no ?

enzief

@enzief

@ubourdon did you implement Format[PositiveDouble] in object PositiveDoubleTag?

Stephen Compall

@S11001001

@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

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