don't we have enough languages?

what is rust?

Rust is a systems programming language that runs blazingly fast, prevents segfaults, and guarantees thread safety.

Shared

Mutable

Concurrent

Choose two!

Memory safety

Intended audience?

Real time computing

Many older languages [are] better than new ones. We keep forgetting already-learned lessons.

[...]

[Rust is] Technology from the past come to save the future from itself

- Graydon Hoare, Creator of Rust at Mozilla

Features

• guaranteed memory safety
• move semantics
• type inference
• zero-cost abstractions
• algebraic data types
• pattern matching
• trait-based generics
• threads without data races
• macros
• minimal runtime
• efficient C bindings
• ...and more!

Guaranteed memory safety

RAII

Memory Safety

fn main() {
    let a:u32;
    println!("Value: {}", a); // a?
}

Example #1a

Memory Safety

fn main() {
    let a:u32 = 1;
    a = 2;
    println!("Value: {}", a);
}

Example #1c

Memory Safety

Example #1e

Memory Safety

#![feature(box_syntax)]
fn create_value() -> Box<u32> {
    let a:Box<u32> = box 2;
    return a;
}

fn main() { 
    let a:u32 = *create_value();
    println!("Value: {}", a);
}

Example #1f

Move semantics

Data can be:

• Moved

• Cloned

• Borrowed

move semantics

#[derive(Debug)]                struct A;
#[derive(Debug, Clone)]         struct B;
#[derive(Debug, Clone, Copy)]   struct C;

fn move_to<T>(v: T) {
    let i_have_stolen_the_v = v;
}

fn main() {
    let a = A; let b = B; let c = C; let d = 3;
    move_to(a);
    println!("a: {:?}", a);  //<-- can't do this!
    move_to(b.clone());  
    println!("b: {:?}", b);
    move_to(c);           
    println!("c: {:?}", c);
    move_to(d);
    println!("d: {:?}", d);
}

Example #2a

move semantics

#[derive(Debug)]
struct A { b: B }
#[derive(Debug, Clone)]
struct B { c: i32 }
 
fn you_can_borrow_this(a: &A) {
    let mut x = (*a).b.clone();
    x = B{ c: x.c * 2 };
    println!("x: {:?}", x);
}
    
fn main() {
    let y = A{ b: B{ c: 3 } };
    you_can_borrow_this(&y);
    println!("y: {:?}", y);
}

Example #2b

Algebraic data types

Product Types

Sum Types

Algebraic data types

#[derive(Debug)]
struct Point {
    x:f32,
    y:f32,
}

fn main() {
    let p = Point {x: 3.0, y: 5.2};
    println!("Value: {:?}", p);
}   

Example #4a

Algebraic data types

struct Point {
    x:f32,
    y:f32,
}

struct NotAPoint {}

#[derive(Debug)]
enum ReturnVal { Point, NotAPoint }

fn main() {
    let p = ReturnVal::NotAPoint;
    println!("Value: {:?}", p);
}

Example #4b

Algebraic data types

#[derive(Debug, Clone)]
enum ReturnVal { Point{ x:f32, y:f32 }, NotAPoint }

fn get_val(input:f32) -> ReturnVal {
    if input > 1.0 {
        ReturnVal::Point{ x: input, y: input} 
    } else { 
        ReturnVal::NotAPoint 
    }
}

fn main() {
    let p = get_val(1.5);
    println!("Value: {:?}", p);
}

Example #4c

Algebraic data types

use std::env;

fn main() {
    let mut args = env::args();
    let exe = args.next(); // Name of app
    let arg1 = args.next(); // Can it be NULL?!??
    println!("{:?}\n{:?}", exe, arg1);
}   

Example #4d

Algebraic data types

use std::fs::File;

fn get_file(filename: &str) -> Result<File, std::io::Error> {
    //let f = try!(File::open(filename));
    let f = File::open(filename)?;
    Ok(f)
}

fn main() {
    match get_file("examples/ex1a.rs") {
        Ok(f) => println!("{:?}", f),
        Err(e) => println!("OOPS! {}", e),
    }
}

Example #4e

Algebraic data types

fn plus_two(v:i32) -> Result<i32, String> { Ok(v + 2) }
fn one_div_by(v:i32) -> Result<i32, String> { 
    if v == 0 { 
        Err("Div by 0".to_string())
    } else { 
        Ok(1 / v) 
    } 
} 
fn times_three(v:i32) -> Result<i32, String> { Ok(v * 3) } 

fn main() {
    let a = Ok(-2)
        .and_then(plus_two)
        .and_then(one_div_by)
        .and_then(times_three);
    println!("{:?}", a);
}

Example #4f

pattern matching

pattern matching

struct Coord {
    x:f32,
    y:f32,
    z:f32,
}

fn main() {
    let c = Coord{ x: 5.0, y: 4.0, z: 3.0 };
    let c2 = (42, 52);
    let Coord { x, z, .. } = c;
    let (x2, y2) = c2;

    println!("Struct x: {}, z: {}", x, z);
    println!("Tuple  x2: {}, y2: {}", x2, y2);
}

Example #5a

pattern matching

fn test_pattern(v: i32) -> () {
    match v {
        a if a > 4 => println!("5 or bigger!"),
        1 ... 2    => println!("1..2"),
        3 | 4      => println!("3|4"),
        _          => println!("Don't know!"),
    }
}   
    
fn main() {
    let _:Vec<()> = (0..)
        .take(6)
        .map(test_pattern)
        .collect();
}

Example #5b

Types and traits

types and traits

#[derive(Debug)]
struct Point { x: f32, y: f32 }

impl Point {
    fn at_x5_and_y10() -> Point {
        Point{x:5.0, y:10.0}
    }   
}

trait Double {
    fn double(&self) -> Self;
}

impl Double for Point {
    fn double(&self) -> Self {
        Point{ x: self.x * 2.0, y: self.y * 2.0}
    }   
}

fn main() {
    let p = Point::at_x5_and_y10();
    println!("Coordinates: {:?}, {:?}", p, p.double());
}

Example #6a

types and traits

use std::convert::From;
use std::ops::Add;

#[derive(Debug)]
struct Celsius(f32);
struct Farenheit(f32);
    
impl From<Farenheit> for Celsius {
    fn from(f:Farenheit) -> Self { Celsius((f.0 - 32.0) * (5.0 / 9.0)) }
}

impl Add for Celsius {
    type Output = Celsius;
    fn add(self, rhs:Celsius) -> Self { Celsius(self.0 + rhs.0) }
}

fn main() { 
    let c = Celsius(37.0);
    let f = Farenheit(95.3);
    println!("Temp sum: {:?}", c + Celsius::from(f));
}

Example #6b

Functional style

functional style

fn main() {
    let mut after_filter = vec!();
    let mut after_mul = vec!();
    let result:i32 = (0..10)
        .filter(|v| v % 2 == 0)
        .map(|v| { after_filter.push(v); v } ) 
        .map(|v| v * 3)
        .map(|v| { after_mul.push(v); v } ) 
        .sum();

    println!("The result is: {}, filter: {:?}, mul: {:?}",
             result,
             after_filter,
             after_mul);
}

Example #7a

Fearless concurrency

Fearless concurrency

use std::sync::mpsc::channel;
use std::thread;
use std::sync::{Arc, Mutex};

const NUM_VALS: u32 = 5;
fn main() {
    let counter = Arc::new(Mutex::new(0));
    let (tx, rx) = channel();
    for i in 0..NUM_VALS {
        let (counter, tx) = (counter.clone(), tx.clone());
        thread::spawn(move || {
            let mut counter = counter.lock().unwrap();
            *counter += 1;
            tx.send(i).unwrap();
        });
    }

    for _ in 0..NUM_VALS {
        print!("{} ", rx.recv().unwrap());
    }
    print!("-> num values: {}", *counter.lock().unwrap());
}

Example #8a

Fearless concurrency

//[...]
fn read_line() -> Poll<String, std::io::Error> {
    sleep!(900);
    to_async!("Value: 42".into())
}

fn parse_line(val: String) -> Poll<i32, std::io::Error> {
    sleep!(400);
    to_async!(read!("Value: {}", val.bytes()))
}

fn main() {
    let start_time = time::Instant::now();
    let mut future = poll_fn(read_line).map(|v| parse_line(v));

    print_time_taken!(start_time.elapsed());
    println!("Val: {:?}", future.poll());
    print_time_taken!(start_time.elapsed());
}

Example #8b

questions?

Further reading:

Slides:                                       https://slides.com/burre83/rust_intro

Code:                        https://github.com/jburell/rust_presentation

into_rust():                                                                    http://intorust.com/

AreWeWebYet?:                                            http://arewewebyet.org/

AreWeIDEYet?:                                             https://areweideyet.com/

TWIR:                                                         https://this-week-in-rust.org/

RustByExample:                                        http://rustbyexample.com/

AwesomeRust:        https://github.com/kud1ing/awesome-rust