The document introduces Kotlin programming concepts such as variables, functions, classes, null safety, collections, and domain-specific languages. It provides code examples to demonstrate Kotlin syntax for these concepts, including defining variables and functions, creating and using classes, handling null values, mapping collections, and building internal domain-specific languages.

1. Derping.with
{ Kotlin }

5. // JVM
// Android
// JavaScript
// LLVM

6. // Actually has libraries
// Actually has tooling
// Actually has traction

7. // Variables

8. val name = "Ross"
var age = 32

9. val name: String = "Ross"
var age: Int = 32

10. val name = "Ross"
var age = 32

11. // Functions

12. fun answer(): Int {
return 42
}

13. fun answer(): Int = 42

14. fun answer() = 42

15. fun answer(): Int {
return 42
}

16. // Parameters

17. fun greet(name: String): String {
return "Hello " + name
}

18. // String Interpolation

19. fun greet(name: String): String {
return "Hello " + name
}

20. fun greet(name: String): String {
return "Hello $name"
}

21. // Named Parameters

22. fun greet(name: String): String {
return "Hello $name"
}

23. fun greet(name: String,
): String {
return "Hello $name"
}

24. fun greet(name: String,
greeting: String = "Hello"
): String {
return "Hello $name"
}

25. fun greet(name: String,
greeting: String = "Hello"
): String {
return "$greeting $name"
}

26. // Calling a function

27. greet("Ross")
greet("Ross", greeting="Aloha")

28. // Classes

29. class Game()
{
}

30. class Game()
{
fun join(user: UserName)
{
}
}

31. val myGame = Game()

32. // Dependencies

33. class Game()
{
fun join(user: UserName)
{
}
}

34. class Game(val logger: Logger)
{
fun join(user: UserName)
{
}
}

35. class Game(val logger: Logger)
{
fun join(user: UserName)
{
this.logger.log("foo")
}
}

36. class Game(val logger: Logger)
{
fun join(user: UserName)
{
logger.log("foo")
}
}

37. class Game(private val logger: Logger)
{
fun join(user: UserName)
{
logger.log("foo")
}
}

38. // Neat Class Things

39. // Neato Constructor Options
// Enums
// Sealed Classes
// Delegation
// Properties
data class Name(val first: String, val last: String)

40. // Null Safety

41. fun greet(name: String): String {
return "Hello $name"
}

42. fun greet(name: String?): String {
return "Hello $name"
}

43. fun greet(name: String?): String {
return "Hello $name"
}
“Hello Ross”

44. fun greet(name: String?): String {
return "Hello $name"
}
“Hello null”

45. fun greet(name: String?): String {
return "Hello $name"
}

46. fun greet(name: String?): String {
return "Hello ${name.toUpperCase()}"
}

47. fun greet(name: String?): String {
return "Hello ${name.toUpperCase()}"
}

48. fun greet(name: String?): String {
return "Hello $name"
}

49. fun greet(name: String?): String {
if (name == null) {
return "STRANGER DANGER"
}
return "Hello $name"
}

50. fun greet(name: String?): String {
return "Hello $name"
}

51. fun greet(name: String?): String {
return "Hello ${formatName(name)}"
}
fun formatName(name: String): String {
return name.toUpperCase();
}

52. fun greet(name: String?): String {
return "Hello ${formatName(name)}"
}
fun formatName(name: String): String {
return name.toUpperCase();
}

53. fun greet(name: String?): String {
return "Hello ${formatName(name)}"
}
fun formatName(name: String): String {
return name.toUpperCase();
}

54. address?.postCode()?.suffix()
age ?: 29

55. // Java Interop

56. import myutils.tableflip
import java.time.LocalDate
val now = LocalDate.now()

57. //Extension Functions

58. fun BoardGame.tableFlip(): String {
return "(ノ°Д° ︵）ノ ┻━┻"
}
val game = BoardGame()
game.tableFlip()

60. fun BoardGame.tableFlip(): String {
return "(ノ°Д° ︵）ノ ┻━┻"
}
val game = BoardGame()
game.tableFlip()

61. import nerdstuff.BoardGame
import myutils.tableflip

62. import java.time.LocalDate
fun LocalDate.yesterday(): LocalDate {
return minusDays(1)
}
val now = LocalDate.now()
val yesterday = now.yesterday()

63. // Collections

64. val nums = listOf(1, 2, 3)
nums.map( )

65. val nums = listOf(1, 2, 3)
nums.map({x: Int -> x * 2})
nums.map({x -> x * 2})
nums.map() {x -> x * 2}
nums.map {x -> x * 2}
nums.map { it * 2 }

66. // DSLs

67. routing {
get("/") {
call.respondText("Hello, world!")
}
post("/register") {
// do stuff
}
}

68. val routing = RoutingBuilder()
routing.get(
{call: Call ->
call.respondText("Hello World!")
}
)
routing.post(/* do stuff */)

69. html {
head {
title { +"Demo" }
}
body {
h1 { +"Welcome!" }
a(href="/FAQ") { +"FAQ" }
}
}

70. // Kotlin & Me & You

71. // Thanks
// @rosstuck
// me@rosstuck.com