Need something where both Clone and Copy work

map_reduce.rs

pub struct Emitter<R,K: Hash + Eq + Clone,V: Copy,MR: MapReduce<R,K,V>> {
    results: HashMap<K,V>
}

impl<R,K: Hash + Eq + Clone,V: Copy,MR: MapReduce<R,K,V>> Emitter<R,K,V,MR> {
    fn new() -> Emitter<R,K,V,MR> {
        Emitter{results: HashMap::with_capacity(25000)}
    }

    #[inline]
    fn emit(&mut self, mr: &mut MR, key: K, value: V) {
        match self.results.entry(key) {
            Vacant(entry) => { entry.set(value); },
            Occupied(mut entry) => {
                let old = *entry.get();
                entry.set(mr.reduce(old, value));
            }
        }
    }

    fn merge(&mut self, mr: &mut MR, other: &Emitter<R,K,V,MR>) {
        for (key,value) in other.results.iter() {
            self.emit(mr, key.clone(), *value);
        }
    }
}

pub trait MapReduce<R,K,V> {
    fn map(&mut self, record: &R, emitter: &mut Emitter<R,K,V,Self>);
    fn reduce(&mut self, val1: V, val2: V) -> V;
}