scalaz 7 equivalent of `<|*|>` from scalaz 6

Question

In Nick Partridge's presentation on deriving scalaz , based on an older version of scalaz, he introduces validations using a function:

def even(x: Int): Validation[NonEmptyList[String], Int] =
  if (x % 2 == 0) x.success else { s"not even: $x".wrapNel.failure }

Then he combines this using

even(1) <|*|> even(2)

which applies the test and returns a validation with the failure message. Using scalaz 7 I get

scala> even(1) <|*|> even(2)
<console>:18: error: value <|*|> is not a member of scalaz.Validation[scalaz.NonEmptyList[String],Int]
       even(1) <|*|> even(2)
               ^

What is the scalaz 7 equivalent of this combinator?

Answer 1

This is now called tuple , so you can write for example:

import scalaz._, Scalaz._

def even(x: Int): Validation[NonEmptyList[String], Int] =
  if (x % 2 == 0) x.success else s"not even: $x".failureNel

val pair: ValidationNel[String, (Int, Int)] = even(1) tuple even(2)

Unfortunately I'm not sure there's a better way to find out this kind of thing than checking out the last 6.0 tag of the source, searching, and then comparing signatures.

Answer 2

You want to use the |@| operator.

scala> (even(1) |@| even(2) |@| even(3)) { (_,_,_) }
<console> Failure(NonEmptyList(not even: 1, not even: 3))

scala> (even(2) |@| even(4) |@| even(6)) { (_,_,_) }
<console> Success((2,4,6))

compare that to tuple operator:

scala> even(1) tuple even(2) tuple even(3)
<console> Failure(NonEmptyList(not even: 1, not even: 3))

scala> even(2) tuple even(4) tuple even(6)
<console> Success(((2,4),6))