Scalaz StateT Trampolines

statetrampoline.scala

package console 
                
import scalaz._, Scalaz._
                
object console extends App {
                
  def countList[T](l: List[T]): Int = {
                
    val i: State[Int, Int] = init[Int]
                
    (l.foldLeft(init[Int].lift[Free.Trampoline]) { (acc, elem) =>
      for {     
        _ <- acc
        f <- modify((i: Int) => i + 1).lift[Free.Trampoline] 
        v <- get.lift[Free.Trampoline]  
      } yield v     
    }).exec(0).run
  }             
                
  val res = countList((1 to 10000).toList)
  println(s"res: ${res}")
}