Lazy dropWhile with Cats

HolyShitThisWorks.scala

package tests

import cats._
import cats.implicits._
import scala.collection.immutable.Stream

/**
  * Created by Yuval.Itzchakov on 3/8/2017.
  */
object Test {
  def dropWhile[F[_]: Foldable : Applicative : MonoidK, A]
  (fa: F[A], pred: (A) => Boolean): Eval[F[A]] = {
    def combine(x: A, xs: Eval[F[A]]): Eval[F[A]] = {
      if (pred(x))
        xs
      else
        xs.map(s => MonoidK[F].algebra.combine(Applicative[F].pure(x), s))
    }

    val base: F[A] = MonoidK[F].empty[A]
    Foldable[F].foldRight(fa, Later(base))(combine)
  }

  def main(args: Array[String]): Unit = {
    val stream = Stream(1,2,3,4,5)
    val list = List(1,2,3,4,5)
    val resStream = dropWhile(stream, (i: Int) => i <= 3)
    val resList = dropWhile(list, (i: Int) => i <= 3)

    println("------- Stream ----------")
    resStream.value.foreach(println)

    println("------- List ---------")
    resList.value.foreach(println)
  }
}