gistfile1.scala

scala> def data(block : Int => Unit) { for(i <- 0 to 10) block(i) }
data: (block: (Int) => Unit)Unit

scala> val x = new Traversable[Int] {                              
     |   def foreach[U](f : Int => U) = {                            
     |     data( f(_) : Unit)                                        
     |   }
     | }
x: java.lang.Object with Traversable[Int] = line15(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)



scala> x.toList.toStream
res6: scala.collection.immutable.Stream[Int] = Stream(0, ?)

scala> x.toStream
java.lang.StackOverflowError
	at $anon$1.thisCollection(<console>:6)
	at scala.collection.TraversableLike$class.toStream(TraversableLike.scala:701)
	at $anon$1.toStream(<console>:6)
	at scala.collection.immutable.Stream.$plus$plus(Stream.scala:141)
	at scala.collection.TraversableLike$class.toStream(TraversableLike.scala:701)
	at $anon$1.toStream(<console>:6)
	at scala.collection.immutable.Stream.$plus$plus(Stream.scala:141)
	at scala.collection.TraversableLike$class.toStream(TraversableLike.scala:701)
	at $anon$1.toStream(<console>:6)
	at scala.collection.immutable.Stream.$plus$plus(Stream.scala:141)
	at scala.collection.TraversableLike$class.toStream(TraversableLike.scala:701)
	at $anon$1.toStream(<console>:6)
	at scala.collection.immutable.Stream.$plus$plus(Stream.scala:141)
	at scal...

http://stackoverflow.com/questions/3797699/generator-block-to-iterator-stream-conversion/3816012#3816012