Defining and invoking a curried function.

Curried.scala

def curriedSum(x: Int)(y: int) = x + y
curriedSum(1)(2)  // 3


def first(x: Int) = (y: Int) => x + y
val second = first(1)
second(2) // 3

// use placeholder notation to use curriedSum in a partially applied function

val onePlus = curriedSum(1)_
onePlus(2) // 3

val twoPlus = curriedSum(2)_
onePlus(2) // 4