def compress[A](list: List[A]): List[(A, Int)] = {
 def compres21(l:List[A],x:A,acc:Int=0): Int = l match {

  case List() => acc
  case head::tail if head == x => compres21(tail,x,acc+1)
  case head::tail if head != x => compres21(tail,x,acc)

 }
 def reduce(l:List[A],x:A,acc:List[A]=List()) : List[A] = l match {
  
  case List() => acc.reverse
  case head::tail if head==x => reduce(tail,x,acc)
  case head::tail if head!=x => reduce(tail,x,head::acc)

 }
 def compress2(l:List[A],acc:List[(A,Int)]=List()) : List[(A,Int)] = l match {
  case List() => acc
  case head::tail => compress2(reduce(tail,head),(head,compres21(head::tail,head))::acc) 
 }
 compress2(list)
}

println(compress(List('a','a','b','c','c','c','d','d','c')))