kotlin.md

Kotlin

Kotlin runs in the Java VM and uses Java types, methods, etc.

• semicolons are optional (so don't use them)

Function Declaration

// Single-line function
fun challenge(x: Int, y: Int, z: Int) = x + y + z

// Multi-line function
fun fermactor(x: Int, y: Int, z: Int): Int {
  // ...
  return x + y + z
}

// Returning lists
// `fun challenge(): MutableList<Int> { ... }` can be changed to:
fun challenge(): List<Int> {
  // ...
  return listOf(1, 2, 3)
}

Logging

// TODO

Variables

var a = 1 // mutable
val b = 2 // immutable
a++ // ++a, --a, etc. same as Java
a += 3 // etc
val a = listOf(1, 2, 3)

Loops

// While
while (x != y); // condition must be boolean (not just int, etc)
while (x != y) ...
while (x != y) { ... }

// List
for (n in arr)

// Range
for (i in 1..5)

Ranges

3..8        // 3 4 5 6 7 8
3..8 step 2 // 3 5 7
8 downto 3  // 8 7 6 5 4 3