AMDG John C. Femiani wrote:
I was just wondering why fusion (and mpl) don't include multi-maps or multi-sets. Are they unnecessary at compile time? Are they too trivial? Do they conceptually not work?
The easiest way to implement a multimap is in terms of an ordinary map. In a fusion/mpl map the key is a type and lookup uses overload resolution. This means that there is necessarily a 1-1 correspondence between keys and values. The obvious way to implement a multimap is to make the value a container. Because of the function nature of fusion/mpl this would be like template<class M, class K, class V> struct multimap_insert_existing { typedef typename insert<typename erase_key<M, K>::type, pair<K, typename push_back<typename at<M, K>::type, V>::type> > type; }; template<class M, class K, class V> struct multimap_insert_new { typedef typename insert<M, pair<K, vector1<V> > > type; }; template<class M, class T> struct multimap_insert { typedef typename T::first key_type; typedef typename T::second value_type; typedef typename eval_if<has_key<M, key_type>, multimap_insert_existing<M, key_type_value_type>, multimap_insert_new<M, key_type, value_type> >::type type; }; In Christ, Steven Watanabe