id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
4857	Boost.Parameter Constructor in Templates Not Supported?	Dean Michael Berris	Daniel Wallin	"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@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
}}}
"	Bugs	new	To Be Determined	parameter	Boost Development Trunk	Problem