Rust 1.84.0-nightly
3fee0f12e

Closures

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

Anonymous functions you can save in a variable or pass as arguments to other functions.

let expensive_closure = |num| {
    println!("calculating slowly...");
    thread::sleep(Duration::from_secs(2));
    num
};

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

• in the current edition: Ch 13.01 — Closures
• In the first edition: Ch 3.23 — Closures