rust

1.rs

use rand::Rng;
use std::cmp::Ordering;
use std::io;
use std::alloc::{*, self};

fn main() {
    println!("Hello, world!");

    let secret_number = rand::thread_rng().gen_range(0..100);

    println!("secret number = {}", secret_number);
    println!("guess a number");

    loop {
        let mut guess = String::new();
        io::stdin().read_line(&mut guess).expect("error!");
        let guess: u32 = match guess.trim().parse() {
            Ok(num) => num,
            Err(_) => continue
        };

        // println!("what you guess in {}", guess);

        match guess.cmp(&secret_number) {
            Ordering::Less => println!("too small"),
            Ordering::Greater => println!("too big"),
            Ordering::Equal => {
                println!("you win!");
                break;
            },
        }
    }
    let mut counter = 0;
    let result = loop {
        counter += 1;
        if counter == 10 {
            break counter * 2;
        }
    };
    // println!("result = {}", result);
}

2.rs

// test use path_glob
use rand::Rng;
use std::cmp::Ordering;
use std::io;
use std::alloc::{*, self};
use std::alloc::{*, {self, *, {{*}}}};
use std::alloc::{{self, GlobalAlloc, Layout}};

3.rs

fn main() {
    println!("secret number = {{123}} {}", secret_number);
    println!("guess a number");
    format!("test"); // => "test"
    format!("hello {}", "world!"); // => "hello world!"
    format!("x = {:?}, y = {val}", 10, val = 30); // => "x = 10, y = 30"
    let (x, y) = (1, 2);
    format!("{x} + {y} = 3"); // => "1 + 2 = 3"
    println!("Name: {0}, Age: {1}", name, age);
    println!("Value: {:>5}", value);
    println!("Pi: {:.2}", pi);
    println!("Pi: {:<8.2e}", pi);
    println!("Value: {:5}", value);
    println!("Pi: {:<8.2}", pi);
    println!("Value: {:<+5}", value);
    println!("{number:0>width$}", number=1, width=5); // TODO
    println!("{number:0<5}", number=1); // TODO
}

4.rs

use std::io;
use std::io::Write;

use serde_json::ser::{Formatter, PrettyFormatter};

pub(crate) struct MyFormatter {
    pretty_formatter: PrettyFormatter<'static>,
}

impl MyFormatter {
    pub(crate) fn new() -> Self {
        MyFormatter {
            pretty_formatter: PrettyFormatter::new(),
        }
    }
}

impl Formatter for MyFormatter {
    fn begin_array<W: ?Sized + Write>(&mut self, writer: &mut W) -> io::Result<()> {
        self.pretty_formatter.begin_array(writer)
    }

    fn end_array<W: ?Sized + Write>(&mut self, writer: &mut W) -> io::Result<()> {
        self.pretty_formatter.end_array(writer)
    }

    fn begin_array_value<W: ?Sized + Write>(
        &mut self,
        writer: &mut W,
        first: bool,
    ) -> io::Result<()> {
        self.pretty_formatter.begin_array_value(writer, first)
    }

    fn end_array_value<W: ?Sized + Write>(&mut self, writer: &mut W) -> io::Result<()> {
        self.pretty_formatter.end_array_value(writer)
    }
}

5.rs

fn main() {
    // 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;

    // Error! The type of a variable can't be changed.
    mutable = true;

    // Variables can be overwritten with shadowing.
    let mutable = true;
}

6.rs

use std::fmt::{self, Formatter, Display};

struct City {
    name: &'static str,
    // Latitude
    lat: f32,
    // Longitude
    lon: f32,
}

impl Display for City {
    // `f` is a buffer, and this method must write the formatted string into it.
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let lat_c = if self.lat >= 0.0 { 'N' } else { 'S' };
        let lon_c = if self.lon >= 0.0 { 'E' } else { 'W' };

        // `write!` is like `format!`, but it will write the formatted string
        // into a buffer (the first argument).
        write!(f, "{}: {:.3}°{} {:.3}°{}",
               self.name, self.lat.abs(), lat_c, self.lon.abs(), lon_c)
    }
}

#[derive(Debug)]
struct Color {
    red: u8,
    green: u8,
    blue: u8,
}

fn main() {
    for city in [
        City { name: "Dublin", lat: 53.347778, lon: -6.259722 },
        City { name: "Oslo", lat: 59.95, lon: 10.75 },
        City { name: "Vancouver", lat: 49.25, lon: -123.1 },
    ] {
        println!("{}", city);
    }
    for color in [
        Color { red: 128, green: 255, blue: 90 },
        Color { red: 0, green: 3, blue: 254 },
        Color { red: 0, green: 0, blue: 0 },
    ] {
        // Switch this to use {} once you've added an implementation
        // for fmt::Display.
        println!("{:?}", color);
    }
}

7.rs

fn main() {
    // 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

    // Scientific notation
    println!("1e4 is {}, -2.5e-3 is {}", 1e4, -2.5e-3);

    // 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);
}

8.rs

fn main() {
    // In general, the `{}` will be automatically replaced with any
    // arguments. These will be stringified.
    println!("{} days", 31);

    // Positional arguments can be used. Specifying an integer inside `{}`
    // determines which additional argument will be replaced. Arguments start
    // at 0 immediately after the format string.
    println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob");

    // As can named arguments.
    println!("{subject} {verb} {object}",
             object="the lazy dog",
             subject="the quick brown fox",
             verb="jumps over");

    // Different formatting can be invoked by specifying the format character
    // after a `:`.
    println!("Base 10:               {}",   69420); // 69420
    println!("Base 2 (binary):       {:b}", 69420); // 10000111100101100
    println!("Base 8 (octal):        {:o}", 69420); // 207454
    println!("Base 16 (hexadecimal): {:x}", 69420); // 10f2c
    println!("Base 16 (hexadecimal): {:X}", 69420); // 10F2C

    // You can right-justify text with a specified width. This will
    // output "    1". (Four white spaces and a "1", for a total width of 5.)
    println!("{number:>5}", number=1);

    // You can pad numbers with extra zeroes,
    println!("{number:0>5}", number=1); // 00001
    // and left-adjust by flipping the sign. This will output "10000".
    println!("{number:0<5}", number=1); // 10000

    // You can use named arguments in the format specifier by appending a `$`.
    println!("{number:0>width$}", number=1, width=5);

    // Rust even checks to make sure the correct number of arguments are used.
    println!("My name is {0}, {1} {0}", "Bond");
    // FIXME ^ Add the missing argument: "James"

    // Only types that implement fmt::Display can be formatted with `{}`. User-
    // defined types do not implement fmt::Display by default.

    #[allow(dead_code)] // disable `dead_code` which warn against unused module
    struct Structure(i32);

    // This will not compile because `Structure` does not implement
    // fmt::Display.
    // println!("This struct `{}` won't print...", Structure(3));
    // TODO ^ Try uncommenting this line

    // For Rust 1.58 and above, you can directly capture the argument from a
    // surrounding variable. Just like the above, this will output
    // "    1", 4 white spaces and a "1".
    let number: f64 = 1.0;
    let width: usize = 5;
    println!("{number:>width$}");
}

9.rs

// Derive the `fmt::Debug` implementation for `Structure`. `Structure`
// is a structure which contains a single `i32`.
#[derive(Debug)]
struct Structure(i32);

// Put a `Structure` inside of the structure `Deep`. Make it printable
// also.
#[derive(Debug)]
struct Deep(Structure);

fn main() {
    // Printing with `{:?}` is similar to with `{}`.
    println!("{:?} months in a year.", 12);
    println!("{1:?} {0:?} is the {actor:?} name.",
             "Slater",
             "Christian",
             actor="actor's");

    // `Structure` is printable!
    println!("Now {:?} will print!", Structure(3));

    // The problem with `derive` is there is no control over how
    // the results look. What if I want this to just show a `7`?
    println!("Now {:?} will print!", Deep(Structure(7)));
}

#[derive(Debug)]
struct Person<'a> {
    name: &'a str,
    age: u8
}

fn func() {
    let name = "Peter";
    let age = 27;
    let peter = Person { name, age };

    // Pretty print
    println!("{:#?}", peter);
}

10.rs

// Import (via `use`) the `fmt` module to make it available.
use std::fmt;

// Define a structure for which `fmt::Display` will be implemented. This is
// a tuple struct named `Structure` that contains an `i32`.
struct Structure(i32);

// To use the `{}` marker, the trait `fmt::Display` must be implemented
// manually for the type.
impl fmt::Display for Structure {
    // This trait requires `fmt` with this exact signature.
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // Write strictly the first element into the supplied output
        // stream: `f`. Returns `fmt::Result` which indicates whether the
        // operation succeeded or failed. Note that `write!` uses syntax which
        // is very similar to `println!`.
        write!(f, "{}", self.0)
    }
}
use std::fmt; // Import `fmt`

// A structure holding two numbers. `Debug` will be derived so the results can
// be contrasted with `Display`.
#[derive(Debug)]
struct MinMax(i64, i64);

// Implement `Display` for `MinMax`.
impl fmt::Display for MinMax {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // Use `self.number` to refer to each positional data point.
        write!(f, "({}, {})", self.0, self.1)
    }
}

// Define a structure where the fields are nameable for comparison.
#[derive(Debug)]
struct Point2D {
    x: f64,
    y: f64,
}

// Similarly, implement `Display` for `Point2D`.
impl fmt::Display for Point2D {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // Customize so only `x` and `y` are denoted.
        write!(f, "x: {}, y: {}", self.x, self.y)
    }
}

fn main() {
    let minmax = MinMax(0, 14);

    println!("Compare structures:");
    println!("Display: {}", minmax);
    println!("Debug: {:?}", minmax);

    let big_range =   MinMax(-300, 300);
    let small_range = MinMax(-3, 3);

    println!("The big range is {big} and the small is {small}",
             small = small_range,
             big = big_range);

    let point = Point2D { x: 3.3, y: 7.2 };

    println!("Compare points:");
    println!("Display: {}", point);
    println!("Debug: {:?}", point);

    // Error. Both `Debug` and `Display` were implemented, but `{:b}`
    // requires `fmt::Binary` to be implemented. This will not work.
    // println!("What does Point2D look like in binary: {:b}?", point);
}

11.rs

use std::fmt; // Import the `fmt` module.

// Define a structure named `List` containing a `Vec`.
struct List(Vec<i32>);

impl fmt::Display for List {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // Extract the value using tuple indexing,
        // and create a reference to `vec`.
        let vec = &self.0;

        write!(f, "[")?;

        // Iterate over `v` in `vec` while enumerating the iteration
        // count in `count`.
        for (count, v) in vec.iter().enumerate() {
            // For every element except the first, add a comma.
            // Use the ? operator to return on errors.
            if count != 0 { write!(f, ", ")?; }
            write!(f, "{}", v)?;
        }

        // Close the opened bracket and return a fmt::Result value.
        write!(f, "]")
    }
}

fn main() {
    let v = List(vec![1, 2, 3]);
    println!("{}", v);
}

12.rs

// 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 (int_param, bool_param) = pair;

    (bool_param, int_param)
}

// The following struct is for the activity.
#[derive(Debug)]
struct Matrix(f32, f32, f32, f32);

fn main() {
    // 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 (more than 12 elements) 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);
}

13.rs

use std::mem;

// 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 main() {
    // 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]);

    // Example of empty slice `&[]`:
    let empty_array: [u32; 0] = [];
    assert_eq!(&empty_array, &[]);
    assert_eq!(&empty_array, &[][..]); // Same but more verbose

    // Arrays can be safely accessed using `.get`, which returns an
    // `Option`. This can be matched as shown below, or used with
    // `.expect()` if you would like the program to exit with a nice
    // message instead of happily continue.
    for i in 0..xs.len() + 1 { // Oops, one element too far!
        match xs.get(i) {
            Some(xval) => println!("{}: {}", i, xval),
            None => println!("Slow down! {} is too far!", i),
        }
    }

    // Out of bound indexing on array causes compile time error.
    //println!("{}", xs[5]);
    // Out of bound indexing on slice causes runtime error.
    //println!("{}", xs[..][5]);
}

14.rs

// 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` variant 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` variant.
        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 main() {
    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);
}

enum VeryVerboseEnumOfThingsToDoWithNumbers {
    Add,
    Subtract,
}

// Creates a type alias
type Operations = VeryVerboseEnumOfThingsToDoWithNumbers;

fn main() {
    // We can refer to each variant via its alias, not its long and inconvenient
    // name.
    let x = Operations::Add;
}

enum VeryVerboseEnumOfThingsToDoWithNumbers {
    Add,
    Subtract,
}

impl VeryVerboseEnumOfThingsToDoWithNumbers {
    fn run(&self, x: i32, y: i32) -> i32 {
        match self {
            Self::Add => x + y,
            Self::Subtract => x - y,
        }
    }
}

15.rs

// An attribute to hide warnings for unused code.
#![allow(dead_code)]

enum Status {
    Rich,
    Poor,
}

enum Work {
    Civilian,
    Soldier,
}

fn main() {
    // Explicitly `use` each name so they are available without
    // manual scoping.
    use crate::Status::{Poor, Rich};
    // Automatically `use` each name inside `Work`.
    use crate::Work::*;

    // Equivalent to `Status::Poor`.
    let status = Poor;
    // Equivalent to `Work::Civilian`.
    let work = Civilian;

    match status {
        // Note the lack of scoping because of the explicit `use` above.
        Rich => println!("The rich have lots of money!"),
        Poor => println!("The poor have no money..."),
    }

    match work {
        // Note again the lack of scoping.
        Civilian => println!("Civilians work!"),
        Soldier  => println!("Soldiers fight!"),
    }
}

16.rs

// An attribute to hide warnings for unused code.
#![allow(dead_code)]

// 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 main() {
    // `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);
}

17.rs

use crate::List::*;

enum List {
    // Cons: Tuple struct that wraps an element and a pointer to the next node
    Cons(u32, Box<List>),
    // Nil: A node that signifies the end of the linked list
    Nil,
}

// Methods can be attached to an enum
impl List {
    // Create an empty list
    fn new() -> List {
        // `Nil` has type `List`
        Nil
    }

    // Consume a list, and return the same list with a new element at its front
    fn prepend(self, elem: u32) -> List {
        // `Cons` also has type List
        Cons(elem, Box::new(self))
    }

    // Return the length of the list
    fn len(&self) -> u32 {
        // `self` has to be matched, because the behavior of this method
        // depends on the variant of `self`
        // `self` has type `&List`, and `*self` has type `List`, matching on a
        // concrete type `T` is preferred over a match on a reference `&T`
        // after Rust 2018 you can use self here and tail (with no ref) below as well,
        // rust will infer &s and ref tail.
        // See https://doc.rust-lang.org/edition-guide/rust-2018/ownership-and-lifetimes/default-match-bindings.html
        match *self {
            // Can't take ownership of the tail, because `self` is borrowed;
            // instead take a reference to the tail
            Cons(_, ref tail) => 1 + tail.len(),
            // Base Case: An empty list has zero length
            Nil => 0
        }
    }

    // Return representation of the list as a (heap allocated) string
    fn stringify(&self) -> String {
        match *self {
            Cons(head, ref tail) => {
                // `format!` is similar to `print!`, but returns a heap
                // allocated string instead of printing to the console
                format!("{}, {}", head, tail.stringify())
            },
            Nil => {
                format!("Nil")
            },
        }
    }
}

fn main() {
    // Create an empty linked list
    let mut list = List::new();

    // Prepend some elements
    list = list.prepend(1);
    list = list.prepend(2);
    list = list.prepend(3);

    // Show the final state of the list
    println!("linked list has length: {}", list.len());
    println!("{}", list.stringify());
}

18.rs

// Globals are declared outside all other scopes.
static LANGUAGE: &str = "Rust";
const THRESHOLD: i32 = 10;

fn is_big(n: i32) -> bool {
    // Access constant in some function
    n > THRESHOLD
}

fn main() {
    let n = 16;

    // Access constant in the main thread
    println!("This is {}", LANGUAGE);
    println!("The threshold is {}", THRESHOLD);
    println!("{} is {}", n, if is_big(n) { "big" } else { "small" });

    // Error! Cannot modify a `const`.
    THRESHOLD = 5;
    // FIXME ^ Comment out this line
}

19.rs

use std::convert::From;

let my_str = "hello";
let my_string = String::from(my_str);


#[derive(Debug)]
struct Number {
    value: i32,
}

impl From<i32> for Number {
    fn from(item: i32) -> Self {
        Number { value: item }
    }
}

fn main() {
    let num = Number::from(30);
    println!("My number is {:?}", num);
}

use std::convert::Into;

#[derive(Debug)]
struct Number {
    value: i32,
}

impl Into<Number> for i32 {
    fn into(self) -> Number {
        Number { value: self }
    }
}

fn main() {
    let int = 5;
    // Try removing the type annotation
    let num: Number = int.into();
    println!("My number is {:?}", num);
}

20.rs

use std::convert::TryFrom;
use std::convert::TryInto;

#[derive(Debug, PartialEq)]
struct EvenNumber(i32);

impl TryFrom<i32> for EvenNumber {
    type Error = ();

    fn try_from(value: i32) -> Result<Self, Self::Error> {
        if value % 2 == 0 {
            Ok(EvenNumber(value))
        } else {
            Err(())
        }
    }
}

fn main() {
    // TryFrom

    assert_eq!(EvenNumber::try_from(8), Ok(EvenNumber(8)));
    assert_eq!(EvenNumber::try_from(5), Err(()));

    // TryInto

    let result: Result<EvenNumber, ()> = 8i32.try_into();
    assert_eq!(result, Ok(EvenNumber(8)));
    let result: Result<EvenNumber, ()> = 5i32.try_into();
    assert_eq!(result, Err(()));
}