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Version: 2.0.x

How to Interop with Scalaz 7.x?

ZIO Instances

If you are a happy Scalaz 7.2 user interop-scala7x module offers ZIO instances for several typeclasses.


import scalaz._, Scalaz._
import zio.interop.scalaz72._

type Database = IList[User]

def findUser(id: UserId): ZIO[Database, UserError, User] = ...
def findUsers(ids: IList[UserId]): ZIO[Database, UserError, IList[User]] = ids.traverse(findUser(_))

ZIO parallel Applicative instance

Due to Applicative and Monad coherence law ZIO's Applicative instance has to be implemented in terms of bind hence when composing multiple effects using Applicative they will be sequenced. To cope with that limitation ZIO tagged with Parallel has an Applicative instance which is not Monad and operates in parallel.


import scalaz._, Scalaz._
import zio.interop.scalaz72._

case class Dashboard(details: UserDetails, history: TransactionHistory)

def getDetails(id: UserId): ZIO[Database, UserError, UserDetails] = ...
def getHistory(id: UserId): ZIO[Database, UserError, TransactionHistory] = ...

def buildDashboard(id: UserId): ZIO[Database, UserError, Dashboard] =
Tag.unwrap(^(par(getDetails(id)), par(getHistory(id)))(Dashboard.apply))

def par[R, E, A](io: ZIO[R, E, A]): scalaz72.ParIO[R, E, A] = Tag(io)