Scala Hello World and Basics

Hello.scala

package com.example

object Hello {
  // 0 - Functions
  def printHelloWorld = println("Hello, world!")
  def add5(num: Int): Int = num + 5
  def add(a: Int, b: Int): Int = a + b
  def sub(a: Int, b: Int) = a - b

  // 1 - Looping
  def multipleOf5(count: Int) = 1 to count map { i => i * 5 }
  def add5(nums: Seq[Int]): Seq[Int] = nums map { n => add5(n) }
  val add2 = (nums: Seq[Int]) => nums.map(_ + 2)

  def printNumbers(nums: Seq[Int]): Unit  = nums foreach { n => print(n) }
  def printNumbers2(nums: Seq[Int]): Unit = nums foreach(print)
  def printStrings(strs: Seq[String]): Unit = strs foreach println

  def total = (nums: Seq[Int]) => nums.fold(0)((total, curr) => total + curr)
  //def add2Total(nums: Seq[Int]): Int = total(add2(nums))
  val add2Total = total compose add2

  // 2 - conditionals
  def isEven(num: Int): Boolean = if (num % 2 == 0) true else false
  def isOdd(num: Int): Boolean = !isEven(num)

  def isOddStr(num: Int): String = if (num % 2 != 0) "odd" else "even"

  def count(num: Int): String = num match {
    case n if n < 0 => "Negatif"
    case 0 => "Nol"
    case 1 => "Satu"
    case 2 => "Dua"
    case _ => "Banyak"
  }

  // 3 - Loop + conditionals
  /*
  def fizzBuzz(num: Int): Seq[String] = 1 to num map { n =>
    n match {
      case x if x % 3 == 0 && x % 5 == 0 => "FizzBuzz"
      case x if x % 3 == 0               => "Fizz"
      case x if x % 5 == 0               => "Buzz"
      case x                             => x.toString
    }
  }
  */

  def fizzBuzz(num: Int): Seq[String] = 1 to num map {
    case x if x % 3 == 0 && x % 5 == 0 => "FizzBuzz"
    case x if x % 3 == 0               => "Fizz"
    case x if x % 5 == 0               => "Buzz"
    case x                             => x.toString
  }

  def main(args: Array[String]): Unit = {
    printHelloWorld

    println(add5(15))
    println(add(10, 20))
    println(sub(10, 20))

    println(multipleOf5(5))
    println(add5(Seq(1, 2, 3, 4, 5)))

    printNumbers(Seq(2, 3, 4, 5, 6))
    println
    printNumbers2(Seq(4, 5, 6, 7, 8, 9))
    println

    println(total(Seq(1, 2, 3, 4)))
    printNumbers2(add2(Seq(1, 2, 3, 4)))
    println
    println(add2Total(Seq(1, 2, 3, 4)))

    println(isEven(2))
    println(isEven(3))
    println(isEven(4))
    println(isEven(5))
    println
    println(isOdd(2))
    println(isOdd(3))
    println(isOdd(4))
    println(isOdd(5))
    println
    println(isOddStr(2))
    println(isOddStr(3))
    println(isOddStr(4))
    println(isOddStr(5))
    println
    println(count(0))
    println(count(-1))
    println(count(1))
    println(count(2))
    println(count(10))
    println(count(100))
    println
    printStrings(fizzBuzz(100))
  }
}

yang bikin sedikit terkejut itu variable yang tiba2 muncul di dalam { } nya map dan variable _ nya plus yang fold sepertinya perlu dijelasin dikit.
kalau audiencenya dari yang terbiasa coding imperative bisa dikasi perbandingan contoh codenya tuh, yang imperatif sama versi deklaratifnya.