val list = 1 to 9
list: scala.collection.immutable.Range.Inclusive = Range 1 to 9
// 根据条件拆分成2部分
println(list.partition(_<5))
(Vector(1, 2, 3, 4),Vector(5, 6, 7, 8, 9))



list.groupBy(_%3)
scala.collection.immutable.Map[Int,scala.collection.immutable.IndexedSeq[Int]] = Map(1 -> Vector(1, 4, 7), 2 -> Vector(2, 5, 8), 0 -> Vector(3, 6, 9))



grouped sliding 

val a = List(1,2,3,4,5,6,7,8)
a: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8)

a.sliding(3,2).foreach(println)
List(1, 2, 3)
List(3, 4, 5)
List(5, 6, 7)
List(7, 8)

a.sliding(3,1).foreach(println)
List(1, 2, 3)
List(2, 3, 4)
List(3, 4, 5)
List(4, 5, 6)
List(5, 6, 7)
List(6, 7, 8)

a.grouped(3).foreach(println)
List(1, 2, 3)
List(4, 5, 6)
List(7, 8)

def sliding(size: Int, step: Int): Iterator[C] 
def grouped(size: Int): Iterator[C]

sliding 滑动窗口 
size 窗口大小
step 步长