P10 =- Run-length encoding of a list.

scala> def encode[T] (l :List[T]) : List[(Int, T)] = {

    pack(l).map(sublist => (sublist.length, sublist.head))
}

     |      |      |      | encode: [T](List[T])List[(Int, T)]
scala> encode(List(‘a, ‘a, ‘a, ‘a, ‘b, ‘c, ‘c, ‘a, ‘a, ‘d, ‘e, ‘e, ‘e, ‘e))
res3: List[(Int, Symbol)] = List((4,’a), (1,’b), (2,’c), (2,’a), (1,’d), (4,’e))