---
date: 2020-10-06
id: 8c351588-1dc2-4955-86b5-a13181367cf9
title: Rust Pattern Syntax
---
# Examples
## Matching Literals
``` rust
fn main() {
let x = 1;
match x {
1 => println!("one"),
2 => println!("two"),
3 => println!("three"),
_ => println!("anything"),
}
}
```
## Matching Named Variables
``` rust
fn main() {
let x = Some(5);
let y = 10;
match x {
Some(50) => println!("Got 50"),
Some(y) => println!("Matched, y = {:?}", y),
_ => println!("Default case, x = {:?}", x),
}
println!("at the end: x = {:?}, y = {:?}", x, y);
}
```
## Multiple Patterns
``` rust
fn main() {
let x = 1;
match x {
1 | 2 => println!("one or two"),
3 => println!("three"),
_ => println!("anything"),
}
}
```
## Matching Ranges of Values with ..=
``` rust
fn main() {
let x = 5;
match x {
1..=5 => println!("one through five"),
_ => println!("something else"),
}
}
```
``` rust
fn main() {
let x = 'c';
match x {
'a'..='j' => println!("early ASCII letter"),
'k'..='z' => println!("late ASCII letter"),
_ => println!("something else"),
}
}
```
## Destructuring
### Destructuring to break apart Values
1. Destructuring Structs
``` rust
struct Point {
x: i32,
y: i32,
}
fn main() {
let p = Point { x: 0, y: 7 };
let Point { x: a, y: b } = p;
assert_eq!(0, a);
assert_eq!(7, b);
}
```
1. Shorthand version
``` rust
struct Point {
x: i32,
y: i32,
}
fn main() {
let p = Point { x: 0, y: 7 };
let Point { x, y } = p;
assert_eq!(0, x);
assert_eq!(7, y);
}
```
```{=org}
#+RESULTS:
```
### Destructuring and matching literal values in one pattern
``` rust
struct Point {
x: i32,
y: i32,
}
fn main() {
let p = Point { x: 0, y: 7 };
match p {
Point { x, y: 0 } => println!("On the x axis at {}", x),
Point { x: 0, y } => println!("On the y axis at {}", y),
Point { x, y } => println!("On neither axis: ({}, {})", x, y),
}
}
```
### Destructuring Enums
[Enums](20200902150714-enums) can also be deconstructed:
``` rust
enum Message {
Quit,
Move { x: i32, y: i32 },
Write(String),
ChangeColor(i32, i32, i32),
}
fn main() {
let msg = Message::ChangeColor(0, 160, 255);
match msg {
Message::Quit => println!("The Quit variant has no data to destructure."),
Message::Move { x, y } => {
println!("Move in the x direction {} and in the y direction {}", x, y);
}
Message::Write(text) => println!("Text message: {}", text),
Message::ChangeColor(r, g, b) => {
println!("Change the color to red {}, green {}, and blue {}", r, g, b)
}
}
}
```
### Destructuring nested Structs and Enums
Nested [structs](20200831193417-structs) and
[enums](20200902150714-enums) can also be destructured:
``` rust
enum Color {
Rgb(i32, i32, i32),
Hsv(i32, i32, i32),
}
enum Message {
Quit,
Move { x: i32, y: i32 },
Write(String),
ChangeColor(Color),
}
fn main() {
let msg = Message::ChangeColor(Color::Hsv(0, 160, 255));
match msg {
Message::ChangeColor(Color::Rgb(r, g, b)) => {
println!("Change the color to red {}, green {}, and blue {}", r, g, b)
}
Message::ChangeColor(Color::Hsv(h, s, v)) => println!(
"Change the color to hue {}, saturation {}, and value {}",
h, s, v
),
_ => (),
}
}
```
### Destructuring Structs and Tuples
``` rust
fn main() {
struct Point {
x: i32,
y: i32,
}
let ((feet, inches), Point { x, y }) = ((3, 10), Point { x: 3, y: -10 });
}
```
## Ignoring Values in a Pattern
### \_
1. Ignoring an entire Value with \_
``` rust
fn foo(_: i32, y: i32) {
println!("This code only uses the y parameter: {}", y);
}
fn main() {
foo(3, 4);
}
```
2. Ignoring parts of a Value with a nested \_
``` rust
fn main() {
let mut setting_value = Some(5);
let new_setting_value = Some(10);
match (setting_value, new_setting_value) {
(Some(_), Some(_)) => {
println!("Can't overwrite an existing customized value");
}
_ => {
setting_value = new_setting_value;
}
}
println!("setting is {:?}", setting_value);
}
```
``` rust
fn main() {
let numbers = (2, 4, 8, 16, 32);
match numbers {
(first, _, third, _, fifth) => println!("Some numbers: {}, {}, {}", first, third, fifth),
}
}
```
3. Ignoring an unused Variable by starting its name with \_
``` rust
fn main() {
let _x = 5;
}
```
```{=org}
#+RESULTS:
```
### …
1. Ignoring remaining parts of a Value with …
``` rust
fn main() {
struct Point {
x: i32,
y: i32,
z: i32,
}
let origin = Point { x: 0, y: 0, z: 0 };
match origin {
Point { x, .. } => println!("x is {}", x),
}
}
```
``` rust
fn main() {
let numbers = (2, 4, 8, 16, 32);
match numbers {
(first, .., last) => {
println!("Some numbers: {}, {}", first, last);
}
}
}
```
## Extra conditionals with Match Guards
``` rust
fn main() {
let num = Some(4);
match num {
Some(x) if x < 5 => println!("less than five: {}", x),
Some(x) => println!("{}", x),
None => (),
}
}
```
``` rust
fn main() {
let x = Some(5);
let y = 10;
match x {
Some(50) => println!("Got 50"),
Some(n) if n == y => println!("Matched, n = {}", n),
_ => println!("Default case, x = {:?}", x),
}
println!("at the end: x = {:?}, y = {}", x, y);
}
```
``` rust
fn main() {
let x = 4;
let y = false;
match x {
4 | 5 | 6 if y => println!("yes"),
_ => println!("no"),
}
}
```
## @ Bindings
``` rust
fn main() {
enum Message {
Hello { id: i32 },
}
let msg = Message::Hello { id: 5 };
match msg {
Message::Hello {
id: id_variable @ 3..=7,
} => println!("Found an id in range: {}", id_variable),
Message::Hello { id: 10..=12 } => println!("Found an id in another range"),
Message::Hello { id } => println!("Found some other id: {}", id),
}
}
```