[Boost-users] [fusion] result_of

I'm very interested in fusion and have been experimenting with it. There is one thing that is currently confusing me. (OK more than one thing). The documentation a typical function at .../fusion/sequence/concepts/associative_sequence.html shows valid expression has_key<K>(s) returning type result_of::has_key::type which is OK by me. But why doesn't fusion use: #include then use boost::result_of::type which would seem to me to reduce the size of fusion (and the docs) by around 50%. What am I missing here? Robert Ramey