Learn Rust 🦀

Variables are declared like this:

let port: u16 = 8333; // unsigned 16-bit integer

Rust has many types (these are only some):

u8, u16, u32, u64, u128 // unsigned integers
i8, i16, i32, i64, i128 // signed integers

usize, isize // machine address sized integers

f32, f64 // floating-point numbers

bool // boolean true or false

char // unicode characters

Changing a variable will not work:

let port: u16 = 8333;
port = 8334; // error: cannot assign twice to immutable variable `port`

Because we first have to declare it as mutable:

let mut port: u16 = 8333;
port = 8334; // works now

You can drop the type and Rust will infer it:

let mut port = 8333;
port = 8334; // still works

Use an ampersand to get a reference, and a star to dereference:

let port = 8333;
let port_ref = &port;

println!("{}", *port_ref); // 8333

This is an array:

let ports = [8333, 8334, 8335];

If you need a big array, use a shorthand notation:

let ports = [0; 1000]; // 1k length filled with zeros

Arrays are not too fun because their length is part of its type and fixed at compile time. If you need a variable-length array, use a vector instead:

let mut ports = vec![8333, 8334];
ports.push(8335);

Loop through a vector using its iterator:

for port in ports.iter() {
  println!("port is: {}", port);
}

Rust has two types of strings:

let name1 = "Bitcoin";             // this is a `&str`
let name2 = "Bitcoin".to_string(); // this is a `String`

A &str is a slice that points to a valid UTF-8 sequence, whereas a String is stored as a vector of bytes that can grow:

fn print_and_return_count(name: &str) -> usize { // received as a `&str`
  println!("String is {}", name);
  name.chars().count()
}

let name = "Bitcoin".to_string(); // this is a `String`
let count = print_and_return_count(&name);

println!("{} is {} char(s) long", name, count);

// Output:
// String is Bitcoin
// Bitcoin is 7 char(s) long

Rust has the concept of ownership:

let name = "Bitcoin".to_string();
let new_name = name;

// error: the value has moved from `name` to `new_name`
println!("{}", name);

Therefore, you have to copy the value if you'd like to use it:

let name = "Bitcoin".to_string();
let new_name = name.clone();