...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::proto::plus_assign::impl
// In header: <boost/proto/traits.hpp> template<typename Expr, typename State, typename Data> struct impl : proto::pass_through<plus_assign>::template impl<Expr, State, Data> { };