stream.scala

scala> def f(x:Int) = {println(x); x+1}
f: (x: Int)Int

scala> val bad = Stream(f(1), f(2), f(3), f(4))
1
2
3
4
bad: scala.collection.immutable.Stream[Int] = Stream(2, ?)

scala> val good=f(1)#::f(2)#::f(3)#::f(4)#::Stream.empty
1
good: scala.collection.immutable.Stream[Int] = Stream(2, ?)

scala>