00_result.txt

✘╹◡╹✘ < sbt run
[info] Set current project to scala-playground (in build file:/Users/aereal/devel/src/github.com/aereal/scala-playground/)
[info] Compiling 1 Scala source to /Users/aereal/devel/src/github.com/aereal/scala-playground/target/scala-2.11/classes...
[error] /Users/aereal/devel/src/github.com/aereal/scala-playground/App.scala:7: not found: type ?
[error]     val v = Applicative[ValidationNel[String, ?]]
[error]                                               ^
[error] /Users/aereal/devel/src/github.com/aereal/scala-playground/App.scala:7: scalaz.ValidationNel[String,<error>] takes no type parameters, expected: one
[error]     val v = Applicative[ValidationNel[String, ?]]
[error]                         ^
[error] /Users/aereal/devel/src/github.com/aereal/scala-playground/App.scala:7: ambiguous implicit values:
[error]  both value vectorInstance in trait VectorInstances of type => scalaz.Traverse[Vector] with scalaz.MonadPlus[Vector] with scalaz.BindRec[Vector] with scalaz.Zip[Vector] with scalaz.Unzip[Vector] with scalaz.IsEmpty[Vector] with scalaz.Align[Vector]
[error]  and method eitherMonad in trait EitherInstances of type [L]=> scalaz.Traverse[[β]scala.util.Either[L,β]] with scalaz.MonadError[[β]scala.util.Either[L,β],L] with scalaz.BindRec[[β]scala.util.Either[L,β]] with scalaz.Cozip[[β]scala.util.Either[L,β]]
[error]  match expected type scalaz.Applicative[<error>]
[error]     val v = Applicative[ValidationNel[String, ?]]
[error]                        ^
[error] three errors found
[error] (compile:compileIncremental) Compilation failed
[error] Total time: 5 s, completed Jan 5, 2016 1:41:00 AM

App.scala

import scalaz._, std.AllInstances._

object App {
  def parseInt(s: String): Validation[String, Int] = try { Success(s.toInt) } catch { case ex: NumberFormatException => Failure(ex.getMessage) }

  def main(args: Array[String]) = {
    val v = Applicative[ValidationNel[String, ?]]
    val x: ValidationNel[String, Int] =
      v.apply2(parseInt("1.0").toValidationNel, parseInt("2.0").toValidationNel)(_ * _)
  }
}

build.sbt

name         := "scala-playground"
version      := "1.0"
scalaVersion := "2.11.6"

lazy val root = (project in file("."))

libraryDependencies ++= Seq(
  "org.scalaz" %% "scalaz-core" % "7.2.0"
)

resolvers += "scalaz-bintray" at "http://dl.bintray.com/scalaz/releases"

• https://gist.github.com/xuwei-k/b0542b48ef2823b5790a/revisions
• https://github.com/non/kind-projector