Core Enums

Core language enums (Option, Result, etc.)

Option

fn main() {
    // Creating Option
    let some_value: Option<i32> = Some(42);
    let no_value: Option<i32> = None;

    println!("Some: {:?}", some_value);
    println!("None: {:?}", no_value);

    // Checking
    println!("is_some: {}", some_value.is_some());
    println!("is_none: {}", no_value.is_none());

    // Unwrapping
    let val = some_value.unwrap();
    println!("Unwrap: {}", val);

    let val = no_value.unwrap_or(0);
    println!("unwrap_or: {}", val);

    let val = no_value.unwrap_or_else(|| compute_default());
    println!("unwrap_or_else: {}", val);

    // Mapping
    let doubled = some_value.map(|x| x * 2);
    println!("map: {:?}", doubled);

    let none_doubled: Option<i32> = None;
    let doubled = none_doubled.map(|x| x * 2);
    println!("None.map: {:?}", doubled);

    // Chaining
    let result = some_value
        .map(|x| x + 10)
        .filter(|x| *x > 50)
        .map(|x| x.to_string());
    println!("Chain: {:?}", result);
}

fn compute_default() -> i32 {
    println!("Computing default...");
    100
}