Option and Result

Option Definition

enum Option<T> {
    None, // absence of Value
    Some(T), // presemce of value
}

Option is a container type in rust which is used to represent a value which may or may not be present. The compiler will treat an Option value as schrodinger's cat, meaning it does not assume it's presence or absence. So as a programmer we need to instruct the compiler on what to do in each of the case.

How to use an Option

Pattern matching

let v: Option<i32> = Some(5i32);
let z: i32 = v + 10; // FAILS to compile

Instruct what to do on either case

match v {
    Some(num) => num + 10,
    None => ???,
}

In case of missing value you can choose to terminate the program using panic! macro or choose a defualt value.

Panics

match v {
    Some(num) => num + 10,
    None => panic!("Can't proceed further"), 
}

Default behaviour

match v {
    Some(num) => num + 10,
    None => num + 42, // For whatever reason
}

Result Definition

enum Result<T,E> {
    Err(E), // In case of absence of Value, the cause of the error
    Ok(T), // presemce of value, Ok variant tells the computation was successful
}