package greeter

object Chapter5 {

  println("Welcome to the Scala worksheet")       //> Welcome to the Scala worksheet

  /////////////////////////////////////////////////////////////////////////////

  //   CHAPTER 5: FIRST-CLASS FUNCTIONS

  /*

  // Write a function to sumall integers between two given numbers a and b

  def sumInts(a: Int, b: Int): Int =

    if (a > b) 0 else a + sumInts(a + 1, b)

  sumInts(1, 5)

  //Write a function to sum the squares of all integers between two given numbers a and b

  def square(x: Int): Int = x * x

  def sumSquares(a: Int, b: Int): Int =

    if (a > b) 0 else square(a) + sumSquares(a + 1, b)

  square(5)

  //Write a function to sum the powers 2n of all integers n between two given numbers a and b:

  def powerOfTwo(x: Int): Int = if (x == 0) 1 else 2 * powerOfTwo(x - 1)

  def sumPowersOfTwo(a: Int, b: Int): Int =

    if (a > b) 0 else powerOfTwo(a) + sumPowersOfTwo(a + 1, b)

  sumPowersOfTwo(2, 4)

  */

  def sum(f: Int => Int, a: Int, b: Int): Int =

    if (a > b) 0 else f(a) + sum(f, a + 1, b)     //> sum: (f: Int => Int, a: Int, b: Int)Int

  //def sumInts(a: Int, b: Int): Int = sum(id, a, b)

  //def sumInts(a: Int, b: Int): Int = sum((x: Int) => x, a, b)

  def sumInts(a: Int, b: Int): Int = sum(x => x, a, b)

                                                  //> sumInts: (a: Int, b: Int)Int

  //def sumSquares(a: Int, b: Int): Int = sum(square, a, b)

  //def sumSquares(a: Int, b: Int): Int = sum((x: Int) => x * x, a, b)

  def sumSquares(a: Int, b: Int): Int = sum(x => x * x, a, b)

                                                  //> sumSquares: (a: Int, b: Int)Int

  def sumPowersOfTwo(a: Int, b: Int): Int = sum(powerOfTwo, a, b)

                                                  //> sumPowersOfTwo: (a: Int, b: Int)Int

  def id(x: Int): Int = x                         //> id: (x: Int)Int

	def square(x: Int): Int = x * x           //> square: (x: Int)Int

	def powerOfTwo(x: Int): Int = if (x == 0) 1 else 2 * powerOfTwo(x - 1)

                                                  //> powerOfTwo: (x: Int)Int

  // 5.2: Currying

}