Functions returning Functions

In Scala, we can use multiple parameter lists. Before

def sum(f: Int => Int): (Int, Int) => Int = {
     def sumF(a: Int, b: Int): Int =
          if (a > b) 0
          else f(a) + sumF(a+1, b)
     sumF
}

Now, we can turn that into

def sum(f: Int => Int)(a: Int, b: Int): Int =
     if (a>b) 0 else f(a) + sum(f)(a+1, b) 

This way, we can still use sum without the second parameter list such as sum(cube).