I have had some time recently to look through some of the Boost source code, and am finding it an absolute treasure trove of useful techniques and idioms. I'd just like to check out my understanding of afew things, and would appreciate feedback. In spirit\home\phoenix\stl\algorithm\transformation.hpp is this namespace boost { namespace phoenix { namespace impl { struct swap { template <class A, class B> struct result { typedef void type; }; template <class A, class B> void operator()(A& a, B& b) const { using std::swap; swap(a, b); } }; ... Am I correct in thinking that the purpose of this is is too present swap as a 'well-behaved' functor from a phoenix composition point of view, with a nested type member? Also in this snippet, the function operator does 'using std::swap;' then uses 'swap' without quaification, rather than explicitly invoking std::swap. The effect of this (I assume) is to perform full name resolution on swap. Why is this done for swap, but not for any other std identifiers, eg copy? Elsewhere in spirit\home\phoenix\stl\algorithm\detail\begin.hpp is this... namespace boost { namespace phoenix { namespace detail { template<class R> typename range_result_iterator<R>::type begin_(R& r) { return boost::begin(r); } } }} This seems to do nothing other than provide an 'indirection' to calling boost::begin. Is the purpose here to provide a possible opportunity for specialisation? It is, btw, a real pleasure to have the chance to see the code of genuine experts in the field. Thanks in advance, Rob