Control Flow

If/Else

let num = 5;
if num < 3 {
    println!("Less than 3");
} else if num <= 3 && num < 7 {
    println!("In the sweet spot");
} else {
    println!("Greater!");
}

With Options and Results

let config_max = Some(3u8);
let age: Result<u8, _> = "34".parse();
if let Some(max) = config_max {
    println!("The maximum is configured to be {}", max);
} else if let Ok(age) = age {
    println!("Age is {}", age);
}

Loops

Loop

The loop keyword is essentially a while(true) loop, it continues to execute the block until you explicitly tell it to stop.

You can also return values from loops by using break followed by the return value, and setting that equal to a variable.

loop {
    println!("again!");
}

let mut counter = 0;

let result = loop {
    counter += 1;

    if counter == 10 {
        break counter * 2;
    }
};

println!("The result is {result}");

While loops

Pretty much the same as while loops in any other language.

 let mut number = 3;

while number != 0 {
    println!("{number}!");

    number -= 1;
}

println!("LIFTOFF!!!");

For loops

For loops in Rust are always for in loops.

let a = [10, 20, 30, 40, 50];

for element in a {
    println!("the value is: {element}");
}

for number in (1..4).rev() {
    println!("{number}!");
}
println!("LIFTOFF!!!");

Match

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter(UsState),
}

fn value_in_cents(coin: Coin) -> u8 {
    match coin {
        Coin::Penny => 1,
        Coin::Nickel => 5,
        Coin::Dime => 10,
        Coin::Quarter(state) => {
            println!("State quarter from {:?}!", state);
            25
        },
        _ => {
            println("Other!")
        }
    }
}

fn plus_one(x: Option<i32>) -> Option<i32> {
    match x {
        None => None,
        Some(i) => Some(i + 1),
    }
}

// Or
let x = 1;
match x {
    1 | 2 => println!("one or two"),
    3 => println!("three"),
    _ => println!("anything"),
}

// Range
let x = 5;
match x {
    1..=5 => println!("one through five"),
    _ => println!("something else"),
}