s4di - Chapter 2 - Exercises

ExercisesCh2.sc

package chapter2

import math._

object ExercisesCh2 {
  def signum(i: Int) = if (i < 0) -1 else if (i > 0) 1 else 0
                                                  //> signum: (i: Int)Int

  signum(5)                                       //> res0: Int = 1
  signum(-5)                                      //> res1: Int = -1
  signum(0)                                       //> res2: Int = 0

  {}

  var x = ()                                      //> x  : Unit = ()
  var y = 0                                       //> y  : Int = 0
  x = y = 1

  def countdown(n: Int) { for (i <- n to 0 by -1) println(i) }
                                                  //> countdown: (n: Int)Unit
  countdown(5)                                    //> 5
                                                  //| 4
                                                  //| 3
                                                  //| 2
                                                  //| 1
                                                  //| 0
  def prodUnicode(s: String) = {
    var total: Long = 1
    for (c <- s) total *= c
    total
  }                                               //> prodUnicode: (s: String)Long
  prodUnicode("Hello")                            //> res3: Long = 9415087488

  val total = "Hello".foldLeft(1L)(_ * _.toInt)   //> total  : Long = 9415087488

  def prodUnicodeRec(s: String): Long = {
    val tail = s.tail
    s.head.toLong * (if (tail.size == 0) 1 else prodUnicodeRec(s.tail))
  }                                               //> prodUnicodeRec: (s: String)Long
  prodUnicodeRec("Hello")                         //> res4: Long = 9415087488

  def computePow(x: Double, n: Int): Double = {
    if (n == 0) 1
    else if (n < 0) 1 / computePow(x, -n)
    else if (n % 2 == 0) pow(computePow(x, n / 2), 2)
    else x * computePow(x, n - 1)
  }                                               //> computePow: (x: Double, n: Int)Double

  computePow(2, 0)                                //> res5: Double = 1.0
  computePow(2, -1)                               //> res6: Double = 0.5
  computePow(2, 1)                                //> res7: Double = 2.0
  computePow(2, 2)                                //> res8: Double = 4.0
}