Closures in Rust

Anonymous functions that capture their environment.

fn main() {
    let factor = 3;
    let scale = |x: i32| x * factor;

    let mut counter = 0;
    let mut bump = || {
        counter += 1;
        counter
    };
    bump();

    let scaled = scale(10);
    println!("{scaled} {}", bump());
}

How it works

scale captures factor by reference.
A mut closure captures and mutates counter.
Closures are called like ordinary functions.

Keywords and builtins used here

fn
i32
let
main
mut

The run, in numbers

Lines: 14
Characters to type: 195
Tokens: 67
Three-star pace: 100 tpm

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Type this snippet

Step 1 of 3 in Closures & folding, step 6 of 14 in Iterators & closures.

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Closures in other languages

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