LazyFib.scala

object LazyFib {
  implicit def wrapStreamInt(s:Stream[Int]) = new StreamWrapper[Int](s)
  def apply(n:Int):List[Int] = fibs().takeN(n)
  def zipWith(f:(Int,Int) => Int, l1:Stream[Int], l2:Stream[Int]):Stream[Int] = { 
    l1.zip(l2).map{x:(Int,Int) => f(x._1, x._2)}
  }
  def fibs():Stream[Int] = Stream.cons(0, Stream.cons(1, zipWith((x:Int,y:Int) => x+y, fibs, fibs.tail)))
}

class StreamWrapper[A](val value:Stream[A]) {
  def takeN(i:Int):List[A] = { 
    var list:List[A] = Nil 
    for(x <- 0 to i) list = list ::: List(value(x))
    list
  }
}