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266 lines
6.4 KiB
Markdown
266 lines
6.4 KiB
Markdown
---
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language: rust
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contributors:
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- ["P1start", "http://p1start.github.io/"]
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filename: learnrust.rs
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---
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Rust is an in-development programming language developed by Mozilla Research.
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It is relatively unique among systems languages in that it can assert memory
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safety *at compile time*. Rust’s first alpha release occurred in January
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2012, and development moves so quickly that at the moment the use of stable
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releases is discouraged, and instead one should use nightly builds.
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Although Rust is a relatively low-level language, Rust has some functional
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concepts that are generally found in higher-level languages. This makes
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Rust not only fast, but also easy and efficient to code in.
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```rust
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// This is a comment. Single-line look like this...
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/* ...and multi-line comment look like this */
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///////////////
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// 1. Basics //
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///////////////
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// Functions
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fn add2(x: int, y: int) -> int {
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// Implicit return (no semicolon)
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x + y
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}
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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: int = 1;
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// Integer/float suffixes
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let y: int = 13i;
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let f: f64 = 1.3f64;
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// Type inference
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let implicit_x = 1i;
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let implicit_f = 1.3f64;
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// Maths
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let sum = x + y + 13i;
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// Mutable variable
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let mut mutable = 1;
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mutable += 2;
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// Strings //
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// String literals
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let x: &'static 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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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 pointer to a string - it doesn’t
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// actually contain the characters of a string, just a pointer to
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// something that does (in this case, `s`)
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let s_slice: &str = s.as_slice();
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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: [int, ..4] = [1, 2, 3, 4];
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// A dynamically-sized vector
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let mut vector: Vec<int> = 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: &[int] = vector.as_slice();
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println!("{} {}", vector, slice); // [1, 2, 3, 4, 5] [1, 2, 3, 4, 5]
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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: int,
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y: int,
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}
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let origin: Point = Point { x: 0, y: 0 };
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// Tuple struct
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struct Point2(int, int);
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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 = Up;
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// Enum with fields
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enum OptionalInt {
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AnInt(int),
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Nothing,
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}
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let two: OptionalInt = AnInt(2);
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let nothing: OptionalInt = 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 get_bar(self) -> T {
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self.bar
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}
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}
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let a_foo = Foo { bar: 1i };
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println!("{}", a_foo.get_bar()); // 1
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// Traits (interfaces) //
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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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println!("{}", a_foo.frobnicate()); // Some(1)
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/////////////////////////
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// 3. Pattern matching //
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/////////////////////////
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let foo = AnInt(1);
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match foo {
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AnInt(n) => println!("it’s an int: {}", n),
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Nothing => println!("it’s nothing!"),
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}
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// Advanced pattern matching
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struct FooBar { x: int, y: OptionalInt }
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let bar = FooBar { x: 15, y: AnInt(32) };
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match bar {
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FooBar { x: 0, y: AnInt(0) } =>
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println!("The numbers are zero!"),
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FooBar { x: n, y: AnInt(m) } if n == m =>
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println!("The numbers are the same"),
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FooBar { x: n, y: AnInt(m) } =>
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println!("Different numbers: {} {}", n, m),
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FooBar { x: _, y: 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 = [1i, 2, 3];
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for i in array.iter() {
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println!("{}", i);
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}
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for i in range(0u, 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 1i == 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 1i == 1 {
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println!("The universe is operating normally.");
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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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}
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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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let mut mine: Box<int> = box 3;
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*mine = 5; // dereference
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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 error
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// Reference - an immutable pointer that refers to other data
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let mut var = 4i;
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var = 3;
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let ref_var: &int = &var;
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println!("{}", var); // Unlike `box`, `var` can still be used
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println!("{}", *ref_var);
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// var = 5; // this would error
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// *ref_var = 6; // this would too
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// Mutable reference
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let mut var2 = 4i;
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let ref_var2: &mut int = &mut var2;
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*ref_var2 += 2;
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println!("{}", *ref_var2); // 6
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// var2 = 2; // this would error
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}
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```
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## Further reading
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There’s a lot more to Rust—this is just the basics of Rust so you can
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understand the most important things. To learn more about Rust, read [The Rust
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Guide](http://doc.rust-lang.org/guide.html) and check out the
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[/r/rust](http://reddit.com/r/rust) subreddit. The folks on the #rust channel
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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
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[Rust playpen](http://play.rust-lang.org) or on the main
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[Rust website](http://rust-lang.org).
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