curry.scala

// Creates a curried version of sum, where the
// first function is that to be applied to the input and  the
// second function is the input
// (Int => Int) => (Int, Int) => Int
def sumCurry(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
}

// Or with syntax sugar.....
def sumCurry(f: Int => Int)(a: Int, b: Int): Int =
  if (a > b) 0 else f(a) + sumCurry(f)(a + 1, b)

// Sum can now be called like this. Pretty clean right?!
sumCurry(cube)(1, 6)
sumCurry(factorial)(1, 6)