Today I spent a lot of time to figure out why some code was not working and I found that it was because I have added the same key more than once on a ValueMap, I was expecting getting back the last added value but no and till I found this problem a lot of time passed (I learned a bit more about U++ internals) but it was not fun.

Looking a the ValueMap implementation the ideal place to do it would be on the function "Add" but it is not virtual so I was thinking that adding a new type "VALUEMAPUNIQUE_V" and modify the "Add" function to:

void ValueMap::Add(const Value& key, const Value& value) {
	Data& d = Clone();
        if(data->GetType() == VALUEMAPUNIQUE_V)
        {
           ///check if key already exists and throw an Exception
        }
	d.key.Add(key);
	d.value.Add(value);
}

What U++ users think about have a ValueMap variant like this ?

Cheers !