Scala の filterNot が遅延評価されない (Scala 2.11.8)

filterNot.scala

$ scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_74).
Type in expressions for evaluation. Or try :help.
scala> val s = (1 to 10).toStream
s: scala.collection.immutable.Stream[Int] = Stream(1, ?)

scala> s.map(s => {println(" " + s); s}).filter(_ % 2 == 0).foreach(println)
 1
 2
2
 3
 4
4
 5
 6
6
 7
 8
8
 9
 10
10

scala> s.map(s => {println(" " + s); s}).filterNot(_ % 2 == 0).foreach(println)
 1
 2
 3
 4
 5
 6
 7
 8
 9
 10
1
3
5
7
9