Mutability

[Jomy10]

Variables

Immutable variables will be declared using let. Mutable variables with var.

let imm = 5
var mut: i64 = 7

Functions

Consider the following example:

struct SomeStruct {
    field: i32
}

ext SomeStruct {
    func someFunc() {
        // func body
    }
}

someFunc can be a static function, non-mutating instance function or a mutating instance function.

There are multiple ways to express this.

For example, Rust takes the following route:

fn static()
fn non_mutating(&self)
fn mutating(&mut self)

Swift takes the following approach:

static func static()
func nonMutating()
mutating func mutating()

Both approaches are explicit. What I like about the Rust approach is the explicit self as an "argument". This makes it very comprehensible that you should access the instance variables using self.field.