fwdlist 0.2.0

use std::mem;


#[derive(Debug)]
struct S {
    v: i32,
    n: Option<Box<S>>,
}

struct I<'a> {
    p: &'a mut Option<Box<S>>,
}

fn inplace<'a, 'b, T, F>(r: &'a mut &'b mut T, mut f: F)
    where F: for<'c> FnMut(&'c mut T) -> &'c mut T {
        unsafe {
            let tmp_ref: *mut T = &mut **r;
            let new_ref = f(&mut *tmp_ref);
            *r = new_ref;
        }
}

trait Animal {
    fn kind(&self) -> &str;
}

struct Dog;
impl Animal for Dog {
    fn kind(&self) -> &str { "dog" }
}
struct Cat;
impl Animal for Cat {
    fn kind(&self) -> &str { "cat" }
}

fn what_kind1(a: &Animal) {
    println!("{:?}", a.kind());
}

fn what_kind2<A: Animal>(a: &A) {
    println!("{:?}", a.kind());
}

fn main() {
    let a = Dog;
    let b = Cat;
    what_kind1(&a);
    what_kind1(&b);
    what_kind2(&a);
    what_kind2(&b);

    //let mut m = M{a: 42, b: 10};

    //let mut n = Box::new(S{ v: 3, n: None });
    //let mut n = Box::new(S{ v: 2, n: Some(n) });
    //let mut n = Box::new(S{ v: 1, n: Some(n) });
    //let mut l = Some(n);

    //println!("{:#?}", l);
    //{
        //let mut i = I{ p: &mut l };
        //let mut i = &mut i;
        //loop {
            //let mut stop = true;
            //inplace(&mut i.p, |p| {
                //if let &mut Some(ref mut node_box) = p {
                    //println!("-> {:?}", node_box.v);
                    //stop = false;
                    //&mut node_box.n
                //} else {
                    //p
                //}
            //});
            //if stop {
                //break
            //}
        //}
    //}
    //println!("{:#?}", l);


    //let mut a = Box::new(42);
    //let mut cc = Box::new(21);

    //let mut b = &mut *a;
    //let mut c = &mut *cc;

    //inplace(&mut &mut *b, |b| {
        //c
    //});
}