[rust/en] Add an English Rust tutorial

Fixes #480.

rust.html.markdown

@@ -0,0 +1,245 @@
+---
+language: rust
+contributors:
+    - ["P1start", "http://p1start.github.io/"]
+filename: learnrust.rs
+---
+
+Rust is an in-development programming language developed by Mozilla Research.
+It is relatively unique among systems languages in that it can assert memory
+safety *at compile time*. Rust’s first alpha release occurred in January
+2012, and development moves so quickly that at the moment the use of stable
+releases is discouraged, and instead one should use nightly builds.
+
+Although Rust is a relatively low-level language, Rust 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.
+
+```rust
+// This is a comment. Single-line look like this...
+/* ...and multi-line comment look like this */
+
+///////////////
+// 1. Basics //
+///////////////
+
+// Functions
+fn add2(x: int, y: int) -> int {
+    // Implicit return (no semicolon)
+    x + y
+}
+
+// Main function
+fn main() {
+    // Numbers //
+
+    // Immutable bindings
+    let x: int = 1;
+
+    // Integer/float suffixes
+    let y: int = 13i;
+    let f: f64 = 1.3f64;
+
+    // Type inference
+    let implicit_x = 1i;
+    let implicit_f = 1.3f64;
+
+    // Maths
+    let sum = x + y + 13i;
+
+    // Mutable variable
+    let mut mutable = 1;
+    mutable += 2;
+
+    // Strings //
+    
+    // String literals
+    let x: &'static str = "hello world!";
+
+    // Printing
+    println!("{} {}", f, x); // 1.3 hello world
+
+    // A `String`
+    let s: String = "hello world".to_string();
+
+    // A string slice - a view into another string
+    let s_slice: &str = s.as_slice();
+
+    //////////////
+    // 2. Types //
+    //////////////
+    
+    // Struct
+    struct Point {
+        x: int,
+        y: int,
+    }
+
+    let origin: Point = Point { x: 0, y: 0 };
+
+    // Tuple struct
+    struct Point2(int, int);
+
+    let origin2 = Point2(0, 0);
+
+    // Basic C-like enum
+    enum Direction {
+        Left,
+        Right,
+        Up,
+        Down,
+    }
+
+    let up = Up;
+
+    // Enum with fields
+    enum OptionalInt {
+        AnInt(int),
+        Nothing,
+    }
+
+    let two:     OptionalInt = AnInt(2);
+    let nothing: OptionalInt = Nothing;
+
+    // Generics //
+
+    struct Foo<T> { bar: T }
+
+    // This is defined in the standard library as `Option`
+    enum Optional<T> {
+        SomeVal(T),
+        NoVal,
+    }
+
+    // Methods //
+
+    impl<T> Foo<T> {
+        // Methods take an explicit `self` parameter
+        fn get_bar(self) -> T {
+            self.bar
+        }
+    }
+
+    let a_foo = Foo { bar: 1i };
+    println!("{}", a_foo.get_bar()); // 1
+
+    // Traits (interfaces) //
+
+    trait Frobnicate<T> {
+        fn frobnicate(self) -> Option<T>;
+    }
+
+    impl<T> Frobnicate<T> for Foo<T> {
+        fn frobnicate(self) -> Option<T> {
+            Some(self.bar)
+        }
+    }
+
+    println!("{}", a_foo.frobnicate()); // Some(1)
+
+    /////////////////////////
+    // 3. Pattern matching //
+    /////////////////////////
+    
+    let foo = AnInt(1);
+    match foo {
+        AnInt(n) => println!("it’s an int: {}", n),
+        Nothing  => println!("it’s nothing!"),
+    }
+
+    // Advanced pattern matching
+    struct FooBar { x: int, y: OptionalInt }
+    let bar = FooBar { x: 15, y: AnInt(32) };
+
+    match bar {
+        FooBar { x: 0, y: AnInt(0) } =>
+            println!("The numbers are zero!"),
+        FooBar { x: n, y: AnInt(m) } if n == m =>
+            println!("The numbers are the same"),
+        FooBar { x: n, y: AnInt(m) } =>
+            println!("Different numbers: {} {}", n, m),
+        FooBar { x: _, y: Nothing } =>
+            println!("The second number is Nothing!"),
+    }
+
+    /////////////////////
+    // 4. Control flow //
+    /////////////////////
+
+    // `for` loops/iteration
+    let array = [1i, 2, 3];
+    for i in array.iter() {
+        println!("{}", i);
+    }
+
+    for i in range(0u, 10) {
+        print!("{} ", i);
+    }
+    println!("");
+    // prints `0 1 2 3 4 5 6 7 8 9 `
+
+    // `if`
+    if 1i == 1 {
+        println!("Maths is working!");
+    } else {
+        println!("Oh no...");
+    }
+
+    // `if` as expression
+    let value = if true {
+        "good"
+    else {
+        "bad"
+    };
+
+    // `while` loop
+    while 1i == 1 {
+        println!("The universe is operating normally.");
+    }
+
+    // Infinite loop
+    loop {
+        println!("Hello!");
+    }
+
+    /////////////////////////////////
+    // 5. Memory safety & pointers //
+    /////////////////////////////////
+    
+    // Owned pointer - only one thing can ‘own’ this pointer at a time
+    let mut mine: Box<int> = box 3;
+    *mine = 5; // dereference
+    let mut now_its_mine = mine;
+    *now_its_mine += 2;
+    println!("{}", now_its_mine); // 7
+    // println!("{}", mine); // this would error
+
+    // Reference - an immutable pointer that refers to other data
+    let mut var = 4i;
+    var = 3;
+    let ref_var: &int = &var;
+    println!("{}", var); // Unlike `box`, `var` can still be used
+    println!("{}", *ref_var);
+    // var = 5; // this would error
+    // *ref_var = 6; // this would too
+
+    // Mutable reference
+    let mut var2 = 4i;
+    let ref_var2: &mut int = &mut var2;
+    *ref_var2 += 2;
+    println!("{}", *ref_var2); // 6
+    // var2 = 2; // this would error
+}
+```
+
+## Further reading
+
+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 tutorial](http://doc.rust-lang.org/tutorial.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.
+
+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).