Rust 1.84.0-beta.4
202008a1b

Mutability

There is a new edition of the book and this is an old link.

Variables are immutable only by default; we can make them mutable by adding mut in front of the variable name.

let mut x = 5;
println!("The value of x is: {x}");
x = 6;
println!("The value of x is: {x}");

Here are the relevant sections in the new and old books:

• in the current edition: Ch 3.01 — Variables and Mutability
• In the first edition: Ch 3.11 — Mutability