programmieren-in-rust/aufgaben/sheet09/sol1/try-opt.rs

// If we would make this public for everyone, we would need to use absolute
// paths!
macro_rules! try_opt {
    ($e:expr) => {
        match $e {
            ::std::option::Option::Some(v) => v,
            None => return None,
        }
    }
}

macro_rules! name {
    () => ($crate)
}

fn main() {
    println!("{:?}", name!());
    println!("consistent: {:?}", is_home_consistent());
    println!("dummy: {:?}", foo());
}

fn foo() -> Option<u8> {
    let a: u8 = try_opt!(Some(50));
    let b = try_opt!(a.checked_mul(6));

    Some(b / 2)
}

fn is_home_consistent() -> Option<bool> {
    use std::env;

    let home_dir = try_opt!(env::home_dir());
    let home_var = try_opt!(env::var_os("HOME"));

    Some(home_dir == home_var)
}