强制使scala函数产生“副作用”

 1     //
 2     def swap(arr:Array[Int],a:Int,b:Int)={
 3         val tmp = arr(a)
 4         arr(a)=arr(b)
 5         arr(b)=tmp
 6     }
 7 def shuffle(arr:Array[Int])={
 8     val t = new Random()
 9     for(i <- (1 to arr.length-1).toArray.reverse)
10     swap(arr,i,t.nextInt(i+1))
11 }