[rust-dev] Flatten a tree into HashMap, how do I pass a &mut around?

Vladimir Pouzanov farcaller at gmail.com
Sun Jun 15 00:14:55 PDT 2014

I have a tree of Nodes where each node might have a name. I'm trying to
convert the tree into a HashMap of named nodes, but my code is getting
extremely complex due to the fact that I cannot pass &mut HashMap around.

let mut named_nodes = HashMap::new();
let nodes = vec!( ... );
named_nodes = self.collect_node_names(&named_nodes, &nodes);
println!('{}', named_nodes);

fn collect_node_names(&self, map: &HashMap<String, Gc<node::Node>>,
    nodes: &Vec<Gc<node::Node>>) -> HashMap<String, Gc<node::Node>> {
  let mut local_map: HashMap<String, Gc<node::Node>> = HashMap::new();
  for (k,v) in map.iter() {
    local_map.insert(k.clone(), *v);
  for n in nodes.iter() {
    for (k,v) in self.collect_node_names(&local_map, &n.subnodes).iter() {
      local_map.insert(k.clone(), *v);
    match n.name {
      Some(ref name) => {
        if local_map.contains_key(name) {

        } else {
          local_map.insert(name.clone(), *n);
      None => (),

this one works, but it's bloated and slow. Any hints on how to improve the

Vladimir "Farcaller" Pouzanov
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