exercises/src/exercises/linked.md

Linked

Fix (many) errors to make this compile and pass tests:

# #[derive(Clone, Copy)]
struct Node<'a> {
    next: Option<&'a Self>,
    value: &'a str,
}

struct Linked<'a, F> {
    node: Node<'a>,
    callback: &'a mut F,
}

impl<'a, F: FnMut(String)> Linked<'a, F> {
# /*
    fn with(&mut self, value: &str) -> Linked<'_, F> {
        Self {
            node: Node {
                next: Some(self.node),
# */
# fn with<'b>(&'b mut self, value: &'b str) -> Linked<'b, F> {
# Linked {
# node: Node {
# next: Some(&self.node),
                value,
            },
            callback: self.callback,
        }
    }

    fn call(&mut self) {
        let mut node = self.node;
        let mut value = node.value.to_string();
        while let Some(next) = node.next {
            value += next.value;
# /*
            node = next;
        }
        self.callback(value);
# */
# node = *next; }
# (self.callback)(value);
    }
}

// don't change anything below

let mut vec = vec![];

let mut linked = Linked {
    node: Node { next: None, value: "0" },
    callback: &mut |value| vec.push(value),
};

// why does removing code below cause the instantiation to fail?

linked.call();
{
    let mut linked = linked.with("1");
    linked.with("2").call();
    linked.with("3").call();
}
linked.with("4").call();

assert_eq!(vec, ["0", "210", "310", "40"]);