Rust Closures

A closure is an anonymous function that can capture variables from its surroundings: |x| x + 1.

ExampleRust

fn apply<F: Fn(i32) -> i32>(f: F, x: i32) -> i32 {
    f(x)
}

fn make_adder(n: i32) -> impl Fn(i32) -> i32 {
    move |x| x + n
}

fn main() {
    let double = |x| x * 2;
    println!("{}", double(21));

    let factor = 3;
    let times = |x| x * factor; // captures factor
    println!("{}", apply(times, 5));

    let add5 = make_adder(5);
    println!("{}", add5(10));

    let mut counter = 0;
    let mut inc = || {
        counter += 1;
        counter
    };
    inc();
    inc();
    println!("{}", counter);
}

Output

Quick check

What does move do in front of a closure?

Gives the closure ownership of what it capturesMoves the closure to the heapMakes it run faster

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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