hmm.rs

pub struct DedupMap<K, V> {
    map: HashMap<K, V>,
}

impl<K, V> DedupMap<K, V>
    where K: Eq + Hash,
          V: From<usize> + ToOwned<Owned=V> + Clone,
{
    pub fn new() -> DedupMap<K, V> {
        DedupMap {
            map: HashMap::new(),
        }
    }

    pub fn get_id<L>(&mut self, k: L) -> V
        where L: Hash + Eq + AsRef<K> + ToOwned<Owned=K>,
              K: Borrow<L>,
    {
        let key = k.as_ref();
        if let Some(idx) = self.map.get(key.borrow()) {
            return idx.to_owned();
        }

        let idx = V::from(self.map.len());
        self.map.insert(k.to_owned(), idx.clone());
        idx
    }
}