wiki/content/20200923144022-closures.md

---
date: 2020-09-23
id: 8353cf5c-2d2d-480a-b957-0e90da847e1c
title: Rust Closures
---

# Syntax

## Long

``` rust
fn main() {
    let double_closure = |num: u32| -> u32 { 2 * num };

    println!("2 times 3 = {}", double_closure(3));
}
```

## Abbreviated

``` rust
fn main() {
    let double_closure = |num| 2 * num;

    println!("2 times 3 = {}", double_closure(3));
}
```

# Closure variable scope

Unlike [Rust functions](20200827170931-functions_macros) Closures can
capture their environment and access variables from the scope in which
they're defined:

``` rust
fn main() {
    let x = 4;

    let equal_to_x = |z| z == x;

    let y = 4;

    assert!(equal_to_x(y));
}
```