Scalaz 7 Upgrade Notes

Dependencies

• Dependencies are more compartmentalized

"org.scalaz" %% "scalaz-core" % scalazVersion
"org.scalaz" %% "scalaz-concurrent" % scalazVersion
"org.scalaz" %% "scalaz-iteratee" % scalazVersion
"org.scalaz" %% "scalaz-effect" % scalazVersion
"org.scalaz" %% "scalaz-iterv" % scalazVersion
"org.scalaz" %% "scalaz-typelevel" % scalazVersion
"org.scalaz" %% "scalaz-xml" % scalazVersion

Package Structure

• Generic (note: valid but it's better to restrict imports to prevent conflicts with other libraries)

import scalaz._
import Scalaz._

• Syntax imports provide implicits to work with type classes and functions

• Syntax imports (note: there is also scalaz.syntax.all._)

import scalaz.syntax.xyz._ // e.g. import scalaz.syntax.applicative._

• Standard library syntax imports (note: there is also scalaz.syntax.std.all._)

import scalaz.syntax.std.xyz._ // e.g. import scalaz.syntax.std.list._

Validation and \/

• Is not a monad (see the Scalaz thread here)
• Use EitherT rather than ValidationT
• \/ is Scalaz either
• Validation.disjunction converts a validation to a Scalaz either
• Validation.either => Validation.toEither for Scala either
• .left and .right similar to .success and .fail
• \/.fromTryCatch and Validation.fromTryCatch
• Validation ||| => valueOr (||| still exists but the meaning is different)
• ValidationNEL => ValidationNel

Zero

• No longer exists
• Use Monoid

// Example from Newman
type RawBody = Array[Byte]
implicit val RawBodyMonoid: Monoid[RawBody] = Monoid.instance(_ ++ _, Array[Byte]())

• No "default" Monoid[Boolean]
• There is Monoid[Boolean @@ Disjunction] and Monoid[Boolean @@ Conjunction]
• Easier to use Option(xyz) | false rather than ~Option(xyz) for simple cases

MA

• No longer exists
• <|*|> => tuple in ApplySyntax

IO

• scalaz.effects => scalaz.effect
• Included in the effect dependency

"org.scalaz" %% "scalaz-effect" % scalazVersion

• unsafePerformIO => unsafePerformIO()

lift-json-scalaz

• Use lift-json-scalaz7
• Lift version 2.5-RC4+

"net.liftweb" %% "lift-json-scalaz7" % liftVersion

Upgrade Examples

• Newman
• Scaliak
• Scalamachine