RotateN to left : Alternate solution for http://aperiodic.net/phil/scala/s-99/p19.scala

RotateN.scala

Alternate solution for 

http://aperiodic.net/phil/scala/s-99/p19.scala

def rotate[A](n: Int, ls: List[A])=
 if (ls.isEmpty) ls
 else{
  val (first,last)=ls.splitAt((if (n>=0) n else ls.length+n)%ls.length)
  last:::first
 }

val li=List('a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k)

rotate(3,li)                                      //> res1: List[Symbol] = List('d, 'e, 'f, 'g, 'h, 'i, 'j, 'k, 'a, 'b, 'c)
rotate(-2,li)                                     //> res2: List[Symbol] = List('j, 'k, 'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i)
rotate(0,li)                                      //> res3: List[Symbol] = List('a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k)
rotate(li.length+1,li)                            //> res4: List[Symbol] = List('b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k, 'a)