Variables

thp distinguishes between mutable and immutable variables.

Immutable variables

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

let surname = "Doe"
let year_of_birth = 1984

Written after the let keyword but before the variable name.

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

When annotating an immutable variable the let 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 let mut, followed by a variable name and a value.

let mut name = "John"
let mut age = 32

Written after the let mut keywords but before the variable name.

let mut String name = "John"
let mut Int age = 32

When annotating a mutable variable the keyword let is optional. mut is still required.

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