// listmap.rs

struct Node {
    head : int,
    tail : Option<@mut Node>
}

type List = Option<@mut Node> ;

trait Map {
    fn mapr(&self, &fn(int) -> int);
}

trait Filter {
    fn filtr(&self, &fn(int) -> bool);
}

impl Map for List {
    fn mapr(&self, f: &fn(int) -> int) { // Thanks to dbaupp for figuring out why this breaks when called "map"!
        let mut current = *self;
        loop {
            match(current) {
                None => break,
                Some(node) => { node.head = f(node.head); current = node.tail },
            }
        }
    }
}

impl ToStr for List {
    fn to_str(&self) -> ~str { 
        fn elements_to_str(n: @mut Node) -> ~str {
            match (n.tail) {
                None => fmt!("%?", n.head),
                Some(tail) => fmt!("%?, %s", n.head, elements_to_str(tail))
            }
        }
        
        match(*self) {
            None => ~"Null",
            Some(n) => fmt!("[%s]", elements_to_str(n))
        }
    }
}

fn main() {
    let lst : List = Some(@mut Node{head: 1, tail: Some(@mut Node{head : 2, tail: Some(@mut Node{head: 3, tail: None})})});
    println(lst.to_str());
    lst.mapr(|x: int| { x + 1 });
    println(lst.to_str());
    lst.mapr(|x: int| { x * x });
    println(lst.to_str());
    lst.mapr(|x: int| { if x % 2 == 0 { x } else { -x }});
    println(lst.to_str());
}