Declaring Mutable & Immutable Variables in Rust

index.md

Declaring Mutable & Immutable Variables in Rust

We can declare mutable and immutable variables in Rust like so:

let foo = 0; // immutable
let mut bar = 1; // mutable

Note that immutability is the default. To make a variable mutable, we need to use the mut prefix.

fn main() {
    let foo = 0;
    let mut bar = 1;
    bar = 2; // okay to reassign
    foo = 3; // ERROR
}