Scala/sandbox/curry.scala


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object Curry {

  // high order function
  def sum(f: Int => Int, a: Int, b: Int) = {
    def loop(a: Int, acc: Int): Int  =
      if (a > b) acc
      else loop(a + 1, f(a) + acc)
    loop(a, 0)
  }

  // curry version: this function return an (Int, Int) => Int function
  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
  }

  def sumInts   = sumCurry(x => x)
  def sumCubes  = sumCurry(x => x * x)

  def run = {
    println("Curry")
    println(sum(x => x * x, 3, 5))
    println(sumInts(3, 5))
    println(sumCubes(3, 5))
  }

}