Another example with computation order...

ComputationOrder1.scala

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

object ComputationOrder {
  
//// With 3 effects, it fails when I use runNel at the beginning

type C3 = Fx.fx3[State[String,?],Choose,Validate[String,?]]

type Check3[A] = Eff[C3,A]

val p3 : Check3[Int] = pure(3)

import cats.std.list._

val r31 = p3.runChoose.runState("baz").runNel.run
val r32 = p3.runChoose.runState("baz").runNel.run
val r33 = p3.runNel.runChoose.runState("baz").run

//// With 2 effects, it works

type C2 = Fx.fx2[Choose,Validate[String,?]]

type Check2[A] = Eff[C2,A]

val p2 : Check2[Int] = pure(3)

import cats.std.list._

val r21 = p2.runChoose.runNel.run
val r22 = p2.runNel.runChoose.run



}