NowYouAreJustBeingSilly.scala

import scalaz._
import Scalaz._

object Main extends App {
  def foo[A](list: List[Option[Int]]): Int = {
    implicit def plus[A] = new ApplicativePlus[({type λ[A]=Int})#λ] {
      def empty[A] = 0
      def plus[A](a: Int, b: ⇒ Int) = a + b
      def point[A](a: ⇒ A) = a.asInstanceOf[Int]
      def ap[A, B](fa: => Int)(f: => Int): Int = 0

    }
    Foldable[List].compose(Foldable[Option]).collapse[({type λ[A]=Int})#λ, Int](list)
  }

  println(foo[String](List(Option(1), Option(2), Option(3), None, Option(4)))) // 10
}