Variables

thp distinguishes between mutable and immutable variables.

Immutable variables

Defined with val, followed by a variable name and a value.

val surname = "Doe"
val year_of_birth = 1984

Written after the val keyword but before the variable name.

val String surname = "Doe"
val Int year_of_birth = 1984

When annotating an immutable variable the val keyword is optional

// Equivalent to the previous code
String surname = "Doe"
Int year_of_birth = 1984

This means that if a variable has only a datatype, it is immutable.

Defined with var, followed by a variable name and a value.

var name = "John"
var age = 32

Written after the var keywords but before the variable name.

var String name = "John"
var Int age = 32

When annotating a mutable variable the keyword var is still required.

// Equivalent to the previous code
var String name = "John"
var Int age = 32