Kotlin language fundamentals

It is advisable that you have the Kotlin reference documentation available while learning Kotlin. You can find it by clicking on the LEARN link on its homepage or by visiting http://kotlinlang.org/docs/reference/.

We'll cover these topics in this section:

• Defining local variables
• Defining a function
• Kotlin's types
• Loops

Defining local variables

Local variables are defined with either var or val:

    var aMutableNumber = 24
    val anImmutableNumber = 42

The difference is that variables defined with var are mutable, while variables defined with val are immutable. A type can optionally be defined:

    var aMutableString: String = "A type can optionally be specified..."
    val anImmutableString: String = "...no matter whether you are using
                                     var or val"

The available types are discussed later in the Kotlin's types section of this chapter. Variables cannot be assigned to null (nothing) without taking precautions. Kotlin has a unique typing...