add examples from Rust By Example

examples built into 3 separate binaries

src/bin/example1.rs

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+#![allow(dead_code)]
+use std::mem;
+// https://doc.rust-lang.org/rust-by-example/primitives.html
+fn example1 () {
+    // Variables can be type annotated.
+    let logical: bool = true;
+
+    let a_float: f64 = 1.0;  // Regular annotation
+    let an_integer   = 5i32; // Suffix annotation
+
+    // Or a default will be used.
+    let default_float   = 3.0; // `f64`
+    let default_integer = 7;   // `i32`
+
+    // A type can also be inferred from context
+    let mut inferred_type = 12; // Type i64 is inferred from another line
+    inferred_type = 4294967296i64;
+
+    // A mutable variable's value can be changed.
+    let mut mutable = 12; // Mutable `i32`
+    mutable = 21;
+}
+
+// https://doc.rust-lang.org/rust-by-example/primitives/literals.html
+fn example1b() {
+    // Integer addition
+    println!("1 + 2 = {}", 1u32 + 2);
+
+    // Integer subtraction
+    println!("1 - 2 = {}", 1i32 - 2);
+    // TODO ^ Try changing `1i32` to `1u32` to see why the type is important
+
+    // Short-circuiting boolean logic
+    println!("true AND false is {}", true && false);
+    println!("true OR false is {}", true || false);
+    println!("NOT true is {}", !true);
+
+    // Bitwise operations
+    println!("0011 AND 0101 is {:04b}", 0b0011u32 & 0b0101);
+    println!("0011 OR 0101 is {:04b}", 0b0011u32 | 0b0101);
+    println!("0011 XOR 0101 is {:04b}", 0b0011u32 ^ 0b0101);
+    println!("1 << 5 is {}", 1u32 << 5);
+    println!("0x80 >> 2 is 0x{:x}", 0x80u32 >> 2);
+
+    // Use underscores to improve readability!
+    println!("One million is written as {}", 1_000_000u32);
+}
+
+// https://doc.rust-lang.org/rust-by-example/primitives/tuples.html
+// Tuples can be used as function arguments and as return values
+fn reverse(pair: (i32, bool)) -> (bool, i32) {
+    // `let` can be used to bind the members of a tuple to variables
+    let (integer, boolean) = pair;
+
+    (boolean, integer)
+}
+
+// The following struct is for the activity.
+#[derive(Debug)]
+struct Matrix(f32, f32, f32, f32);
+
+fn example1c() {
+    // A tuple with a bunch of different types
+    let long_tuple = (1u8, 2u16, 3u32, 4u64,
+                      -1i8, -2i16, -3i32, -4i64,
+                      0.1f32, 0.2f64,
+                      'a', true);
+
+    // Values can be extracted from the tuple using tuple indexing
+    println!("long tuple first value: {}", long_tuple.0);
+    println!("long tuple second value: {}", long_tuple.1);
+
+    // Tuples can be tuple members
+    let tuple_of_tuples = ((1u8, 2u16, 2u32), (4u64, -1i8), -2i16);
+
+    // Tuples are printable
+    println!("tuple of tuples: {:?}", tuple_of_tuples);
+    
+    // But long Tuples cannot be printed
+    // let too_long_tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
+    // println!("too long tuple: {:?}", too_long_tuple);
+    // TODO ^ Uncomment the above 2 lines to see the compiler error
+
+    let pair = (1, true);
+    println!("pair is {:?}", pair);
+
+    println!("the reversed pair is {:?}", reverse(pair));
+
+    // To create one element tuples, the comma is required to tell them apart
+    // from a literal surrounded by parentheses
+    println!("one element tuple: {:?}", (5u32,));
+    println!("just an integer: {:?}", (5u32));
+
+    //tuples can be destructured to create bindings
+    let tuple = (1, "hello", 4.5, true);
+
+    let (a, b, c, d) = tuple;
+    println!("{:?}, {:?}, {:?}, {:?}", a, b, c, d);
+
+    let matrix = Matrix(1.1, 1.2, 2.1, 2.2);
+    println!("{:?}", matrix);
+}
+
+
+// This function borrows a slice
+fn analyze_slice(slice: &[i32]) {
+    println!("first element of the slice: {}", slice[0]);
+    println!("the slice has {} elements", slice.len());
+}
+
+fn example1d() {
+    // Fixed-size array (type signature is superfluous)
+    let xs: [i32; 5] = [1, 2, 3, 4, 5];
+
+    // All elements can be initialized to the same value
+    let ys: [i32; 500] = [0; 500];
+
+    // Indexing starts at 0
+    println!("first element of the array: {}", xs[0]);
+    println!("second element of the array: {}", xs[1]);
+
+    // `len` returns the count of elements in the array
+    println!("number of elements in array: {}", xs.len());
+
+    // Arrays are stack allocated
+    println!("array occupies {} bytes", mem::size_of_val(&xs));
+
+    // Arrays can be automatically borrowed as slices
+    println!("borrow the whole array as a slice");
+    analyze_slice(&xs);
+
+    // Slices can point to a section of an array
+    // They are of the form [starting_index..ending_index]
+    // starting_index is the first position in the slice
+    // ending_index is one more than the last position in the slice
+    println!("borrow a section of the array as a slice");
+    analyze_slice(&ys[1 .. 4]);
+}
+
+
+fn main() {
+    example1();
+    example1b();
+    example1c();
+    example1d();
+}

src/bin/example2.rs

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+#![allow(dead_code)]
+use std::mem;
+
+// https://doc.rust-lang.org/rust-by-example/custom_types/structs.html
+
+#[derive(Debug)]
+struct Person {
+    name: String,
+    age: u8,
+}
+
+// A unit struct
+struct Unit;
+
+// A tuple struct
+struct Pair(i32, f32);
+
+// A struct with two fields
+struct Point {
+    x: f32,
+    y: f32,
+}
+
+// Structs can be reused as fields of another struct
+struct Rectangle {
+    // A rectangle can be specified by where the top left and bottom right
+    // corners are in space.
+    top_left: Point,
+    bottom_right: Point,
+}
+
+fn example2() {
+    // Create struct with field init shorthand
+    let name = String::from("Peter");
+    let age = 27;
+    let peter = Person { name, age };
+
+    // Print debug struct
+    println!("{:?}", peter);
+
+    // Instantiate a `Point`
+    let point: Point = Point { x: 10.3, y: 0.4 };
+
+    // Access the fields of the point
+    println!("point coordinates: ({}, {})", point.x, point.y);
+
+    // Make a new point by using struct update syntax to use the fields of our
+    // other one
+    let bottom_right = Point { x: 5.2, ..point };
+
+    // `bottom_right.y` will be the same as `point.y` because we used that field
+    // from `point`
+    println!("second point: ({}, {})", bottom_right.x, bottom_right.y);
+
+    // Destructure the point using a `let` binding
+    let Point { x: left_edge, y: top_edge } = point;
+
+    let _rectangle = Rectangle {
+        top_left: Point { x: left_edge, y: top_edge },
+        bottom_right: bottom_right,
+        // struct instantiation is an expression too
+    };
+
+    // Instantiate a unit struct
+    let _unit = Unit;
+
+    // Instantiate a tuple struct
+    let pair = Pair(1, 0.1);
+
+    // Access the fields of a tuple struct
+    println!("pair contains {:?} and {:?}", pair.0, pair.1);
+
+    // Destructure a tuple struct
+    let Pair(integer, decimal) = pair;
+
+    println!("pair contains {:?} and {:?}", integer, decimal);
+}
+
+// https://doc.rust-lang.org/rust-by-example/custom_types/enum.html
+
+// Create an `enum` to classify a web event. Note how both
+// names and type information together specify the variant:
+// `PageLoad != PageUnload` and `KeyPress(char) != Paste(String)`.
+// Each is different and independent.
+enum WebEvent {
+    // An `enum` may either be `unit-like`,
+    PageLoad,
+    PageUnload,
+    // like tuple structs,
+    KeyPress(char),
+    Paste(String),
+    // or c-like structures.
+    Click { x: i64, y: i64 },
+}
+
+// A function which takes a `WebEvent` enum as an argument and
+// returns nothing.
+fn inspect(event: WebEvent) {
+    match event {
+        WebEvent::PageLoad => println!("page loaded"),
+        WebEvent::PageUnload => println!("page unloaded"),
+        // Destructure `c` from inside the `enum`.
+        WebEvent::KeyPress(c) => println!("pressed '{}'.", c),
+        WebEvent::Paste(s) => println!("pasted \"{}\".", s),
+        // Destructure `Click` into `x` and `y`.
+        WebEvent::Click { x, y } => {
+            println!("clicked at x={}, y={}.", x, y);
+        },
+    }
+}
+
+fn example2b() {
+    let pressed = WebEvent::KeyPress('x');
+    // `to_owned()` creates an owned `String` from a string slice.
+    let pasted  = WebEvent::Paste("my text".to_owned());
+    let click   = WebEvent::Click { x: 20, y: 80 };
+    let load    = WebEvent::PageLoad;
+    let unload  = WebEvent::PageUnload;
+
+    inspect(pressed);
+    inspect(pasted);
+    inspect(click);
+    inspect(load);
+    inspect(unload);
+}
+
+// https://doc.rust-lang.org/rust-by-example/custom_types/enum/c_like.html
+// enum with implicit discriminator (starts at 0)
+enum Number {
+    Zero,
+    One,
+    Two,
+}
+
+
+// enum with explicit discriminator
+enum Color {
+    Red = 0xff0000,
+    Green = 0x00ff00,
+    Blue = 0x0000ff,
+}
+
+
+fn example2c() {
+    // `enums` can be cast as integers.
+    println!("zero is {}", Number::Zero as i32);
+    println!("one is {}", Number::One as i32);
+
+    println!("roses are #{:06x}", Color::Red as i32);
+    println!("violets are #{:06x}", Color::Blue as i32);
+}
+
+
+fn main() {
+    println!("Hello World! This is an APE built with Rust.");
+    example2();
+    example2b();
+    example2c();
+    0;
+}