Scala By Example -- usage: compute((x, y) => x * y)(x => x)(1, 3)

ex_5_2_4.scala

import scala.annotation.tailrec

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