Kotlin Koans - Introduction

1 Hello, world!

fun start(): String = "OK"

• Named arguments

fun joinOptions(options: Collection<String>) = options.joinToString(", ","[","]")

• Default arguments

fun foo(name: String, number: Int=42, toUpperCase: Boolean=false) =
        (if (toUpperCase) name.toUpperCase() else name) + number

fun useFoo() = listOf(
        foo("a"),
        foo("b", number = 1),
        foo("c", toUpperCase = true),
        foo(name = "d", number = 2, toUpperCase = true)
)

2 Lambdas

fun containsEven(collection: Collection<Int>): Boolean = collection.any { it%2==0 }