#include <iostream>
#include<boost/parameter/keyword.hpp>
#include<boost/parameter/name.hpp>
#include<boost/parameter/parameters.hpp>

BOOST_PARAMETER_NAME(name)
BOOST_PARAMETER_NAME(index)

struct myclass_impl
{
    template <class ArgumentPack>
    myclass_impl(ArgumentPack const& args)
    {
        std::cout << "name = " << args[_name]
                  << "; index = " << args[_index | 42]
                  << std::endl;
    }
};

struct myclass : myclass_impl
{
    BOOST_PARAMETER_CONSTRUCTOR(
        myclass, (myclass_impl), tag
      , (required (name,*)) (optional (index,*))) // no semicolon
};
int main(int argc, char **argv) {
}

liefert:

/home/andreas/projects/Testboost/main.cpp:23:18: error: expected identifier before ‘(’ token
/home/andreas/projects/Testboost/main.cpp:23:34: error: ‘tag’ is not a type
/home/andreas/projects/Testboost/main.cpp:24:9: error: expected identifier before ‘(’ token
/home/andreas/projects/Testboost/main.cpp:24:19: error: expected ‘)’ before ‘(’ token
/home/andreas/projects/Testboost/main.cpp:24:19: error: expected ‘)’ before ‘(’ token
/home/andreas/projects/Testboost/main.cpp:24:20: error: ‘name’ has not been declared
/home/andreas/projects/Testboost/main.cpp:24:25: error: expected identifier before ‘*’ token
/home/andreas/projects/Testboost/main.cpp:24:26: error: ISO C++ forbids declaration of ‘BOOST_PARAMETER_CONSTRUCTOR’ with no type [-fpermissive]
/home/andreas/projects/Testboost/main.cpp:24:26: error: ‘BOOST_PARAMETER_CONSTRUCTOR’ declared as function returning a function
/home/andreas/projects/Testboost/main.cpp:24:26: error: expected ‘;’ at end of member declaration
/home/andreas/projects/Testboost/main.cpp:24:27: error: expected unqualified-id before ‘)’ token

Wie kann das sein?