struct_list.rs

struct List<T> {
    car: T,
    cdr: Option<Box<List<T>>>,
}


fn main() {
    let mut a = 
        List {
            car: 1i8,
            cdr: Some(Box::new(
                List {
                    car: 2i8,
                    cdr: Some(Box::new(List {car: 3i8, cdr: None})),
                }
            )),
        }; // construction.
    a.cdr = a.cdr.unwrap().cdr;
    println!("{}", a.cdr.unwrap().car)
}