I am aware that variadic macros are not in the current C++ standard. However, it is declared that "the C++ standardization committee is likely to adopt C99's preprocessor extensions for the next version of the C++ standard." So here is a question about it. I have though that with the help of variadic macros, it would be nolonger necessary for us to povide size of preprocessor tuples manually. For instance, in fact it is easy to implement the BOOST_PP_TUPLE_ELEM macro more clearly as: #define TUPLE_ELEM(i, tuple) TUPLE_ELEM_ ## i tuple #define TUPLE_ELEM_0(a0, ...) a0 #define TUPLE_ELEM_1(a0, a1, ...) a1 #define TUPLE_ELEM_2(a0, a1, a2, ...) a2 #define TUPLE_ELEM_3(a0, a1, a2, a3, ...) a3 However, I failed to think out a way to implement TUPLE_SIZE. Is there any way to do this? If the answer is yes, it will be possible to eliminate all the manually specified size argument of all tuple manipulation macros. That would be a great news for preprocessor metaprogramming. Best regards, Zhen -- USTC Alumni Email System