Scala first program issue

Question

I have just started to learn Scala after some experience with functional programming in other languages.

def freq(c:Char, y:String, list:List[(Char,Int)]): List[(Char,Int)] = list match{
  case _ =>  freq(c, y.filter(_ == c), list :: List((count(c,y),c))) 
  case nil => list
} 

In the above code I am getting an error when trying to concatenate the list recursively. The error is occurring in list::List((count(c,y),c)). The count method takes a char and a string and returns an int based on how many times that char occurs.

Any help would be much appreciated. The error I am getting states found [(Char,Int)] required (Char,Int).

Answer 1

Cons operator (::) is an infix operator so if you want to get a type of List[T] and not List[List[T]] then you should write

freq(c, y.filter(_ == c),(count(c,y),c)) :: list)

Answer 2

Also you need to switch the 2 match cases because nil would never be evaluated this way. _ will catch nil too and never continue to reach the second case.