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windyboy
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---
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page-title: "Learn Rust in Y Minutes"
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url: https://learnxinyminutes.com/docs/rust/
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date: "2023-04-02 09:39:01"
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---
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Rust is a programming language developed by Mozilla Research. Rust combines low-level control over performance with high-level convenience and safety guarantees.
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It achieves these goals without requiring a garbage collector or runtime, making it possible to use Rust libraries as a “drop-in replacement” for C.
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Rust’s first release, 0.1, occurred in January 2012, and for 3 years development moved so quickly that until recently the use of stable releases was discouraged and instead the general advice was to use nightly builds.
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On May 15th 2015, Rust 1.0 was released with a complete guarantee of backward compatibility. Improvements to compile times and other aspects of the compiler are currently available in the nightly builds. Rust has adopted a train-based release model with regular releases every six weeks. Rust 1.1 beta was made available at the same time of the release of Rust 1.0.
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Although Rust is a relatively low-level language, it has some functional concepts that are generally found in higher-level languages. This makes Rust not only fast, but also easy and efficient to code in.
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// This is a comment. Line comments look like this...
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// and extend multiple lines like this.
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/// Documentation comments look like this and support markdown notation.
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/// # Examples
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///
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/// \`\`\`
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/// let five = 5
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/// \`\`\`
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///////////////
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// 1. Basics //
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///////////////
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#\[allow(dead\_code)\]
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// Functions
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// \`i32\` is the type for 32-bit signed integers
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fn add2(x: i32, y: i32) \-> i32 {
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// Implicit return (no semicolon)
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x + y
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}
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#\[allow(unused\_variables)\]
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#\[allow(unused\_assignments)\]
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#\[allow(dead\_code)\]
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// Main function
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fn main() {
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// Numbers //
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// Immutable bindings
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let x: i32 \= 1;
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// Integer/float suffixes
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let y: i32 \= 13i32;
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let f: f64 \= 1.3f64;
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// Type inference
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// Most of the time, the Rust compiler can infer what type a variable is, so
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// you don’t have to write an explicit type annotation.
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// Throughout this tutorial, types are explicitly annotated in many places,
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// but only for demonstrative purposes. Type inference can handle this for
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// you most of the time.
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let implicit\_x \= 1;
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let implicit\_f \= 1.3;
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// Arithmetic
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let sum \= x + y + 13;
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// Mutable variable
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let mut mutable \= 1;
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mutable \= 4;
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mutable += 2;
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// Strings //
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// String literals
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let x: &str \= "hello world!";
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// Printing
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println!("{} {}", f, x); // 1.3 hello world
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// A \`String\` – a heap-allocated string
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// Stored as a \`Vec<u8>\` and always hold a valid UTF-8 sequence,
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// which is not null terminated.
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let s: String \= "hello world".to\_string();
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// A string slice – an immutable view into another string
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// This is basically an immutable pair of pointers to a string – it doesn’t
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// actually contain the contents of a string, just a pointer to
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// the begin and a pointer to the end of a string buffer,
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// statically allocated or contained in another object (in this case, \`s\`).
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// The string slice is like a view \`&\[u8\]\` into \`Vec<T>\`.
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let s\_slice: &str \= &s;
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println!("{} {}", s, s\_slice); // hello world hello world
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// Vectors/arrays //
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// A fixed-size array
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let four\_ints: \[i32; 4\] \= \[1, 2, 3, 4\];
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// A dynamic array (vector)
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let mut vector: Vec<i32\> \= vec!\[1, 2, 3, 4\];
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vector.push(5);
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// A slice – an immutable view into a vector or array
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// This is much like a string slice, but for vectors
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let slice: &\[i32\] \= &vector;
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// Use \`{:?}\` to print something debug-style
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println!("{:?} {:?}", vector, slice); // \[1, 2, 3, 4, 5\] \[1, 2, 3, 4, 5\]
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// Tuples //
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// A tuple is a fixed-size set of values of possibly different types
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let x: (i32, &str, f64) \= (1, "hello", 3.4);
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// Destructuring \`let\`
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let (a, b, c) \= x;
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println!("{} {} {}", a, b, c); // 1 hello 3.4
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// Indexing
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println!("{}", x.1); // hello
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//////////////
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// 2. Types //
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//////////////
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// Struct
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struct Point {
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x: i32,
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y: i32,
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}
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let origin: Point \= Point { x: 0, y: 0 };
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// A struct with unnamed fields, called a ‘tuple struct’
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struct Point2(i32, i32);
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let origin2 \= Point2(0, 0);
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// Basic C-like enum
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enum Direction {
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Left,
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Right,
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Up,
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Down,
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}
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let up \= Direction::Up;
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// Enum with fields
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enum OptionalI32 {
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AnI32(i32),
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Nothing,
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}
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let two: OptionalI32 \= OptionalI32::AnI32(2);
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let nothing \= OptionalI32::Nothing;
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// Generics //
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struct Foo<T\> { bar: T }
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// This is defined in the standard library as \`Option\`
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enum Optional<T\> {
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SomeVal(T),
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NoVal,
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}
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// Methods //
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impl<T\> Foo<T\> {
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// Methods take an explicit \`self\` parameter
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fn bar(&self) \-> &T { // self is borrowed
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&self.bar
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}
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fn bar\_mut(&mut self) \-> &mut T { // self is mutably borrowed
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&mut self.bar
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}
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fn into\_bar(self) \-> T { // here self is consumed
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self.bar
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}
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}
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let a\_foo \= Foo { bar: 1 };
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println!("{}", a\_foo.bar()); // 1
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// Traits (known as interfaces or typeclasses in other languages) //
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trait Frobnicate<T\> {
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fn frobnicate(self) \-> Option<T\>;
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}
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impl<T\> Frobnicate<T\> for Foo<T\> {
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fn frobnicate(self) \-> Option<T\> {
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Some(self.bar)
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}
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}
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let another\_foo \= Foo { bar: 1 };
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println!("{:?}", another\_foo.frobnicate()); // Some(1)
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// Function pointer types //
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fn fibonacci(n: u32) \-> u32 {
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match n {
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0 \=> 1,
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1 \=> 1,
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\_ \=> fibonacci(n \- 1) + fibonacci(n \- 2),
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}
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}
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type FunctionPointer \= fn(u32) \-> u32;
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let fib : FunctionPointer \= fibonacci;
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println!("Fib: {}", fib(4)); // 5
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/////////////////////////
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// 3. Pattern matching //
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/////////////////////////
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let foo \= OptionalI32::AnI32(1);
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match foo {
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OptionalI32::AnI32(n) \=> println!("it’s an i32: {}", n),
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OptionalI32::Nothing \=> println!("it’s nothing!"),
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}
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// Advanced pattern matching
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struct FooBar { x: i32, y: OptionalI32 }
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let bar \= FooBar { x: 15, y: OptionalI32::AnI32(32) };
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match bar {
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FooBar { x: 0, y: OptionalI32::AnI32(0) } \=>
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println!("The numbers are zero!"),
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FooBar { x: n, y: OptionalI32::AnI32(m) } if n \== m \=>
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println!("The numbers are the same"),
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FooBar { x: n, y: OptionalI32::AnI32(m) } \=>
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println!("Different numbers: {} {}", n, m),
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FooBar { x: \_, y: OptionalI32::Nothing } \=>
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println!("The second number is Nothing!"),
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}
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/////////////////////
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// 4. Control flow //
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/////////////////////
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// \`for\` loops/iteration
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let array \= \[1, 2, 3\];
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for i in array {
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println!("{}", i);
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}
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// Ranges
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for i in 0u32..10 {
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print!("{} ", i);
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}
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println!("");
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// prints \`0 1 2 3 4 5 6 7 8 9 \`
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// \`if\`
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if 1 \== 1 {
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println!("Maths is working!");
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} else {
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println!("Oh no...");
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}
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// \`if\` as expression
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let value \= if true {
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"good"
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} else {
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"bad"
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};
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// \`while\` loop
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while 1 \== 1 {
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println!("The universe is operating normally.");
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// break statement gets out of the while loop.
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// It avoids useless iterations.
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break
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}
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// Infinite loop
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loop {
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println!("Hello!");
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// break statement gets out of the loop
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break
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}
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/////////////////////////////////
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// 5. Memory safety & pointers //
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/////////////////////////////////
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// Owned pointer – only one thing can ‘own’ this pointer at a time
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// This means that when the \`Box\` leaves its scope, it can be automatically deallocated safely.
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let mut mine: Box<i32\> \= Box::new(3);
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\*mine \= 5; // dereference
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// Here, \`now\_its\_mine\` takes ownership of \`mine\`. In other words, \`mine\` is moved.
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let mut now\_its\_mine \= mine;
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\*now\_its\_mine += 2;
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println!("{}", now\_its\_mine); // 7
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// println!("{}", mine); // this would not compile because \`now\_its\_mine\` now owns the pointer
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// Reference – an immutable pointer that refers to other data
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// When a reference is taken to a value, we say that the value has been ‘borrowed’.
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// While a value is borrowed immutably, it cannot be mutated or moved.
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// A borrow is active until the last use of the borrowing variable.
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let mut var \= 4;
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var \= 3;
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let ref\_var: &i32 \= &var;
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println!("{}", var); // Unlike \`mine\`, \`var\` can still be used
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println!("{}", \*ref\_var);
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// var = 5; // this would not compile because \`var\` is borrowed
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// \*ref\_var = 6; // this would not either, because \`ref\_var\` is an immutable reference
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ref\_var; // no-op, but counts as a use and keeps the borrow active
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var \= 2; // ref\_var is no longer used after the line above, so the borrow has ended
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// Mutable reference
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// While a value is mutably borrowed, it cannot be accessed at all.
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let mut var2 \= 4;
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let ref\_var2: &mut i32 \= &mut var2;
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\*ref\_var2 += 2; // '\*' is used to point to the mutably borrowed var2
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println!("{}", \*ref\_var2); // 6 , // var2 would not compile.
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// ref\_var2 is of type &mut i32, so stores a reference to an i32, not the value.
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// var2 = 2; // this would not compile because \`var2\` is borrowed.
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ref\_var2; // no-op, but counts as a use and keeps the borrow active until here
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}
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There’s a lot more to Rust—this is just the basics of Rust so you can understand the most important things. To learn more about Rust, read [The Rust Programming Language](http://doc.rust-lang.org/book/index.html) and check out the [/r/rust](http://reddit.com/r/rust) subreddit. The folks on the #rust channel on irc.mozilla.org are also always keen to help newcomers.
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You can also try out features of Rust with an online compiler at the official [Rust playpen](http://play.rust-lang.org/) or on the main [Rust website](http://rust-lang.org/).
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Got a suggestion? A correction, perhaps? [Open an Issue](https://github.com/adambard/learnxinyminutes-docs/issues/new) on the Github Repo, or make a [pull request](https://github.com/adambard/learnxinyminutes-docs/edit/master/rust.html.markdown) yourself!
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