[Boost-bugs] [Boost C++ Libraries] #4857: Boost.Parameter Constructor in Templates Not Supported?

Subject: [Boost-bugs] [Boost C++ Libraries] #4857: Boost.Parameter Constructor in Templates Not Supported?
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-11-16 09:13:03

#4857: Boost.Parameter Constructor in Templates Not Supported?
-------------------------------------+--------------------------------------
 Reporter:  mikhailberis             |       Owner:  danielw  
     Type:  Bugs                     |      Status:  new      
Milestone:  To Be Determined         |   Component:  parameter
  Version:  Boost Development Trunk  |    Severity:  Problem  
 Keywords:                           |  
-------------------------------------+--------------------------------------
 If I try to create a Boost.Parameter Constructor as shown in the following
 code listing, I get a handful of errors in the preprocessor code used by
 `BOOST_PARAMETER_CONSTRUCTOR`:

 {{{
     #include <boost/parameter.hpp>

     namespace foo {

         BOOST_PARAMETER_NAME(arg1)
         BOOST_PARAMETER_NAME(arg2)

         template <class Tag>
         struct base {
             template <class ArgPack>
             base(ArgPack const & args)
             : val1(args[_arg1])
             , val2(args[_arg2])
             {}

             int val1,val2;
         };

         template <class Tag>
         struct derived : base<Tag> {
             BOOST_PARAMETER_CONSTRUCTOR(
                 derived, (base<Tag>), tag,
                 (optional (arg1,int,1) (arg2,int,2)))
         };

     } /* foo */

     struct default_ {};

     int main(int argc, char * arg[]) {
         foo::derived<default_> instance();
         return 0;
     }
 }}}

 With GCC 4.4 on Ubuntu Linux I get the following errors:

 {{{
 dean_at_dean-desktop:~/Source/spike$ g++ -o boost_parameter_template
 boost_parameter_template.cpp -I~/boost/
 boost_parameter_template.cpp:24: error: macro
 "BOOST_PARAMETER_FOR_EACH_pred_aux2" passed 3 arguments, but takes just 2
 boost_parameter_template.cpp:24: error: macro "BOOST_PP_SPLIT_0" requires
 2 arguments, but only 1 given
 boost_parameter_template.cpp:24: error: macro "BOOST_PP_SEQ_ELEM_III"
 requires 2 arguments, but only 1 given
 boost_parameter_template.cpp:24: error: macro "BOOST_PP_SEQ_ELEM_III"
 requires 2 arguments, but only 1 given
 boost_parameter_template.cpp:24: error: ‘BOOST_PP_IIF_0’ was not declared
 in this scope
 boost_parameter_template.cpp:24: error: template argument 1 is invalid
 boost_parameter_template.cpp:24: error:
 ‘BOOST_PP_REPEAT_1_BOOST_PP_TUPLE_ELEM_2_0’ does not name a type
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4857>
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