Defines the syntax elements of xpressive's action expressions.

namespace boost {
  namespace xpressive {
    template<typename Fun> struct function;
    template<typename T> struct value;
    template<typename T> struct reference;
    template<typename T> struct local;
    template<typename T, int I = 0, typename Dummy = proto::is_proto_expr> 
      struct placeholder;

    function< op::push >::type const push;
    function< op::push_back >::type const push_back;
    function< op::push_front >::type const push_front;
    function< op::pop >::type const pop;
    function< op::pop_back >::type const pop_back;
    function< op::pop_front >::type const pop_front;
    function< op::top >::type const top;
    function< op::back >::type const back;
    function< op::front >::type const front;
    function< op::first >::type const first;
    function< op::second >::type const second;
    function< op::matched >::type const matched;
    function< op::length >::type const length;
    function< op::str >::type const str;
    function< op::insert >::type const insert;
    function< op::make_pair >::type const make_pair;
     static_cast_;
    () dynamic_cast_;
    ()() const_cast_;
    unspecified check;
    unspecified let;
     BOOST_PROTO_DEFINE_FUNCTION_TEMPLATE(1, as, boost::proto::default_domain, 
                                          (boost::proto::tag::function), 
                                          ((op::as)(typename)));
    template<typename T> reference< T > const ref(T & t);
    template<typename T> reference< T const  > const cref(T const & t);
     BOOST_PROTO_DEFINE_VARARG_FUNCTION_TEMPLATE(construct, 
                                                 boost::proto::default_domain, 
                                                 (boost::proto::tag::function), 
                                                 ((op::construct)(typename)));
    namespace op {
      struct push;
      struct push_back;
      struct push_front;
      struct pop;
      struct pop_back;
      struct pop_front;
      struct front;
      struct back;
      struct top;
      struct first;
      struct second;
      struct matched;
      struct length;
      struct str;
      struct insert;
      struct make_pair;
      template<typename T> struct as;
      template<typename T> struct static_cast_;
      template<typename T> struct dynamic_cast_;
      template<typename T> struct const_cast_;
      template<typename T> struct construct;
      template<typename Except> struct throw_;
    }
  }
}