stupid enum tricks

gistfile1.txt

#[derive(Debug)]
enum List<T,L> {
    Null(T),
    Cell(T,L),
}

use List::*;

type Nil<T> = List<T,()>;
type Single<T> = List<T,Nil<T>>;
type Pair<T> = List<T,Single<T>>;
type Triple<T> = List<T,Pair<T>>;
type Quad<T> = List<T,Triple<T>>;

fn car<T,L>(x: &List<T,L>) -> &T {
    match *x {
        Cell(ref v,_) => v,
        Null(ref v) => v,
    }
}

fn cdr<T,L>(x: &List<T,L>) -> &L {
    match *x {
        Cell(_,ref v) => v,
        Null(_) => unreachable!(),
    }
}

fn main() {

    let f : Nil<u8> = List::Null(0u8);
    let g : Quad<u8> = Cell(1u8,Cell(2u8,Cell(3u8,Cell(4u8,f))));

    println!("{:?}", car(cdr(cdr(&g))));
}