Hello, I have this macro: #define vmacro(expr, ...) \ cout << "n macro = " << BOOST_PP_VARIADIC_SIZE(__VA_ARGS__) << endl; \ cout << BOOST_PP_VARIADIC_ELEM(0, __VA_ARGS__) << endl; \ cout << BOOST_PP_VARIADIC_ELEM(1, __VA_ARGS__) << endl; \ for (int i = 0; i < BOOST_PP_VARIADIC_SIZE(__VA_ARGS__); i++) { \ cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ } The VARIADIC_SIZE is correct and I can access elements using BOOST_PP_VARIADIC_ELEM as long as I use a literal. The loop body produces error messages when compiling. BOOST_PP_VARIADICS is 1. The goal is to concatenate all variadic macro arguments to a string. If there a more clever solution, I'm very eager to hear them. Thanks! Florian ERROR MESSAGES: % clang++ -std=c++11 -g3 -rdynamic -ldl test.cpp test.cpp:154:3: error: expected expression vmacro(4, 5, 6); ^ test.cpp:120:26: note: expanded from macro 'vmacro' cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ ^ /usr/include/boost/preprocessor/variadic/elem.hpp:26:101: note: expanded from macro 'BOOST_PP_VARIADIC_ELEM' # define BOOST_PP_VARIADIC_ELEM(n, ...) BOOST_PP_CAT(BOOST_PP_VARIADIC_ELEM_, n)(__VA_ARGS__,) ^ 1 error generated. g++ -std=c++11 -g3 -rdynamic -ldl test.cpp In file included from test.cpp:9:0: test.cpp: In function 'void f(int)': test.cpp:120:26: error: expected primary-expression before ')' token cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ ^ test.cpp:154:3: note: in expansion of macro 'vmacro' vmacro(4, 5, 6); ^ test.cpp:120:26: error: 'BOOST_PP_VARIADIC_ELEM_i' was not declared in this scope cout << i << ": " << BOOST_PP_VARIADIC_ELEM(i, __VA_ARGS__) << endl; \ ^ test.cpp:154:3: note: in expansion of macro 'vmacro' vmacro(4, 5, 6); ^