object Main {
  import scala.annotation._
  @tailrec
  def unfoldr_foldl[A, B, C](f: A => Option[(A, B)])(a: A)(g: B => C => C)(c: C): C = f(a) match {
     case None => c
     case Some((a, b)) => unfoldr_foldl(f)(a)(g)(g(b)(c))
  }
  def main(args: Array[String]) {
    val a = unfoldr_foldl[Int,String,Int](i => List("1", "2", "3", "end")(i) match {
      case "end" => None
      case s => Some(i + 1, s)
    })(0)(a => b => a.toInt + b)(0)
    println(a)
  }
}
 
 

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