Can't run example of using Eff

[oskoi]

import cats._, data._
import org.atnos.eff._

type ReaderInt[A] = Reader[Int, A]
type WriterString[A] = Writer[String, A]

type Stack = Fx.fx3[WriterString, ReaderInt, Eval]

import org.atnos.eff.all._
import org.atnos.eff.syntax.all._

// useful type aliases showing that the ReaderInt and the WriterString effects are "members" of R
// note that R could have more effects
type _readerInt[R]    = ReaderInt |= R
type _writerString[R] = WriterString |= R

def program[R :_readerInt :_writerString :_eval]: Eff[R, Int] = for {
// get the configuration
  n <- ask[R, Int]

  // log the current configuration value
  _ <- tell("the required power is "+n)

  // compute the nth power of 2
  a <- delay(math.pow(2, n.toDouble).toInt)

  // log the result
  _ <- tell("the result is "+a)
} yield a

// run the action with all the interpreters
// each interpreter running one effect
program[Stack].runReader(6).runWriter.runEval.run

After compilation get:

No instance found for Member[[β$0$]cats.data.Kleisli[[A]A,Int,β$0$], A$A57.this.Stack].
The effect [β$0$]cats.data.Kleisli[[A]A,Int,β$0$] is not part of the stack A$A57.this.Stack
 or it was not possible to determine the stack that would result from removing [β$0$]cats.data.Kleisli[[A]A,Int,β$0$] from A$A57.this.Stack
program[Stack].runReader(6).runWriter.runEval.run;}
                        ^

What i do wrong? I took this example from introduction http://atnos-org.github.io/eff/org.atnos.site.Introduction.html

[etorreborre]

In the Installation part there's a paragraph about the necessary sbt settings, like -Ypartial-unification. Do you have that?

[oskoi]

Oops ... no. Thank you!
Everything worked!