Rust Crash Course - ZtM

• https://youtu.be/lzKeecy4OmQ

Fundamentals

Data Types

• Boolean
• Integer
• Double / Float
• Character
• String

Variables

• assign data to a temporary memory location
  • allows programmer to easily work with memory
• can be set to any value & type (dynamically?)
• immutable by default, but can be mutable

// notice that no data types are used below
let two = 2;
let hello = "hello";
let j = 'j';
let my_half = 0.5;
let mut my_name = "Bill";
let quit_program = false;
let your_half = my_half;

Functions

fn add(a: i32, b: i32) -> i32 {
  a + b
}

• fn: reserved word meaning that we're declaring a function
• add: name of the function
• (a: i32, b: i32): parameters - param: type
• -> i32: return type of the function
• a + b: do the math and return the value (just like in Ruby)

println macro

• macros expand into additional code
• println prints information to the terminal

let life = 42;

// the '!' symbol means that we're calling a macro
println!("hello");

// in "{:?}", the ':?' sequence mean debug print
println!("{:?}", life);
println!("{:?} {:?}", life, life);
println!("the meaning is {:?}", life);

// another notation
println!("{life:?}");

// without the ':?' means it's going to be visible for users
println!("{life}");

Control flow using if

let a = 99;

if a > 200 {
  println!("Huge number");
} else if a > 99 {
  println!("Big number");
} else {
  println!("Small number");
}

• parentheses are not mandatory

Repetition using loops

• types of loops
  • loop - infinite loop
  • while - conditional loop
• both types can exit using break

loop example:

let mut a = 0;

loop {
  if a == 5 {
    break;
  }

  println!("{:?}", a);
  a = a + 1;
}

while example:

let mut a = 0;

while a != 5 {
  println!("{:?}", a);
  a = a + 1;
}

Tool installation

• rustup: https://rustup.rs/
• Visual Studio Code

practice

Download files from: https://links.zerotomastery.io/rust-crash-course

cargo commands:

# run a specific file
# (needs to be at the same directory as Cargo.toml
cargo run --bin ${file}

# run without compiling messages
carg run --bin ${file} -q # or --quiet

The exercises a1, a2, a3a and a3b are pretty trivial.

Match expressions

Here at 1:17:00

• similar to if..else

• exhaustive

  • all options must be accounted for

• looks like a "switch case" statement

• match vs if..else

  • match will be checked by the compiler
    • if a new possibility is added, you will be notified when this occurs
  • if..else is not checked by the compiler
    • if a new possibility is added, your code may contain a bug

NOTE: prefer match over if..else when working with a single variable. It's more robust.

example with boolean:

fn main() {
  let some_bool = true;
  match some_bool {
    true => println!("it's true"),
    false => println!("it's false"),
  }
}

example with int:

fn main() {
  let some_int = 3;
  match some_int {
    1 => println!("it's 1"),
    2 => println!("it's 2"),
    3 => println!("it's 3"),
    // underscore _ works like 'default' in C
    _ => println!("it's something else"),
  }
}

Expressions

https://youtu.be/lzKeecy4OmQ?t=9364

Working With Data

enum

• data that can be one of multiple different possibilities
  • each possibility is called a "variant"
• provides information about your program to the compiler
  • more robust programs when paired with match

enum Direction {
  Up,
  Down,
  Left,
  Right,
}

fn which_way(go: Direction) {
  // remember, with match all possibilities
  // must be satisfied. Therefore, if you
  // add a new item to the Direction enum,
  // the compiler will complain if you don't
  // add it to the match block below.
  match go {
    Direction::Up => "up",
    Direction::Down => "down",
    Direction::Left => "left",
    Direction::Right => "right",
  }
}

struct

• a type containing multiple pieces of data
• each piece of data is called a "field"
• all fields MUST be populated
• make working with data easier

Example:

struct ShippingBox {
  depth: i32,
  width: i32,
  height: i32,
}

fn my_function() {
  let my_box = ShippingBox {
    depth: 3,
    width: 2,
    height: 5,
  };

  // access individual fields with a '.' dot
  let tall = my_box.height;
}

tuples

• a type of "record"
• we consider it an "anonymous struct", meaning: a struct with no name where the fields are also unnamed.
• useful to return pairs of data from functions
• can be destructured easily into variables
• accepts different types
• to access items of a tuple use the . dot followed by the index (kinda unusual notation). example: my_tuple.0

// declaração com inferência de tipo
let numbers = (1, 2, 3);
let my_stuff = (1, 2.3, false);

// declaração com tipagem explícita
let numbers: (i32, i32, i32) = (1, 2, 3);
let my_stuff (i32, f64, bool) = (1, 2.3, false);

// desserialiazação
let (a, b, c) = numbers;

fn one_two_three() -> (i32, i32, i32) {
  (1, 2, 3)
}

let numbers = one_two_three();
let (x, y, z) = one_two_three();

Continuar em #Expressions