Assignment_02/src/main/scala/Main.scala

   1 import scala.annotation.tailrec
   2
   3 object Main {
   4   // Question 1.
   5   // a)
   6   @tailrec
   7   def fac(n: Int, acc: Int = 1) : Int =
   8     if (n == 1) acc else fac(n - 1, acc * n)
   9
  10   // b)
  11   def fib(n: Int) : Int = {
  12     n match {
  13       case 0 => 0
  14       case 1 => 1
  15       case _ => fib(n - 1) + fib(n - 2)
  16     }
  17   }
  18
  19   /*@tailrec
  20   def fibTail(n: Int, acc: Int = 0) : Int = {
  21     def stage()
  22     n match {
  23       case 0 => 0
  24       case 1 => 1
  25       case _ =>
  26     }
  27   }*/
  28
  29   // Question 2.
  30   def sum(f: Double => Double, a: Int, b: Int): Double = {
  31     def iter(a: Int, acc: Double): Double =
  32       if (a > b) acc
  33       else iter(a + 1, acc + f(a))
  34     iter(a, 0.0)
  35   }
  36
  37   // Question 3.
  38   def product(f: Double => Double) (a: Int) (b: Int): Double = {
  39     def iter(a: Int, acc: Double): Double =
  40       if (a > b) acc
  41       else iter(a + 1, acc * f(a))
  42     iter(a, 1.0)
  43   }
  44
  45   // c)
  46   def generalization(init: Double) (reducer: (Double, Double) => Double) (f: Double => Double) (a: Int) (b: Int): Double = {
  47     def iter(a: Int, acc: Double): Double =
  48       if (a > b) acc
  49       else iter(a + 1, reducer(acc, f(a)))
  50     iter(a, init)
  51   }
  52
  53   def main(args: Array[String]) = {
  54     println("Question 1")
  55     println(s"fac(4): ${fac(4)}")
  56     println(s"fib(10): ${fib(4)}")
  57
  58     println("\nQuestion 2")
  59     val sumOfSquares = sum(x => x * x, 2, 4)
  60     println(s"sum of square from 2 to 4 : $sumOfSquares")
  61
  62     println("\nQuestion 3")
  63
  64     def factorial = product (x => x) (1) _
  65     println(s"factorial(4) : ${factorial(4)}")
  66
  67     // def sum2 = generalization (0) ((x, y) => x + y) _ _ _
  68     // def product2 = generalization (1) (_ * _) _ _ _
  69   }
  70 }