calculator
<
   boost::proto::exprns_::basic_expr
   <
      boost::proto::tagns_::tag::multiplies,
      boost::proto::argsns_::list2
      <
         calculator
         <
            boost::proto::exprns_::basic_expr
            <
               boost::proto::tagns_::tag::divides,
               boost::proto::argsns_::list2
               <
                  calculator
                  <
                     boost::proto::exprns_::basic_expr
                     <
                        boost::proto::tagns_::tag::minus,
                        boost::proto::argsns_::list2
                        <
                           calculator
                           <
                              boost::proto::exprns_::expr
                              <
                                 boost::proto::tagns_::tag::terminal,
                                 boost::proto::argsns_::term
                                 <
                                    placeholder<1>
                                 >,
                                 0l
                              >
                           > const&,
                           calculator
                           <
                              boost::proto::exprns_::expr
                              <
                                 boost::proto::tagns_::tag::terminal,
                                 boost::proto::argsns_::term
                                 <
                                    placeholder<0>
                                 >,
                                 0l
                              >
                           > const&
                        >,
                        2l
                     >
                  > const&,
                  calculator
                  <
                     boost::proto::exprns_::expr
                     <
                        boost::proto::tagns_::tag::terminal,
                        boost::proto::argsns_::term
                        <
                           placeholder<1>
                        >,
                        0l
                     >
                  > const&
               >,
               2l
            >
         > const&,
         calculator
         <
            boost::proto::exprns_::basic_expr
            <
               boost::proto::tagns_::tag::terminal,
               boost::proto::argsns_::term<int const&>,
               0l
            >
         >
      >,
      2l
   >
>