Contains definition of proto::domain<> class template and helpers for defining domains with a generator and a grammar for controlling operator overloading.

namespace boost {
  namespace proto {
    template<typename Generator = proto::default_generator, 
             typename Grammar = proto::_> 
      struct domain;
    struct default_domain;
    struct deduce_domain;
    template<typename T> struct is_domain;
    template<typename T> struct domain_of;
  }
}