Scala By Example

ex_5_2_1.scala

import scala.annotation.tailrec

def sum(f: Int => Int)(a: Int, b: Int) : Int = {
  @tailrec
  def iter(a: Int, result: Int) : Int = {
    if (a > b) result
    else iter(a + 1, f(a) + result)
  }
  iter(a, 0)
}