Stream_lazy_eval.scala

scala> def a(x: Int) = {println("evaluated"); x * 100 }
a: (x: Int)Int

scala> val s : Stream[Int] = 1 #:: 2 #:: 3 #:: a(100) #:: Stream.empty
s: Stream[Int] = Stream(1, ?)


scala> s(0)
res0: Int = 1

scala>  s.foreach(println)
1
2
3
evaluated
10000