Hi all, I don't think that reentrancy mechanism is working for this macro. Is it supposed to? The following example illustrates my problem (I tried both automatic and manual methods): #include <boost/preprocessor/seq/for_each_i.hpp> #define seq\ ((1)(2)(3))\ ((4)(5)(6))\ ((7)(8)(9)) #define MACRO(r, data, i, elem)\ BOOST_PP_SEQ_FOR_EACH_I(MACRO2, ~, elem) #define MACRO1(r, data, i, elem)\ BOOST_PP_SEQ_FOR_EACH_I_R(r, MACRO2, ~, elem) #define MACRO2(r, data, i, elem)\ elem BOOST_PP_SEQ_FOR_EACH_I(MACRO, ~, seq) BOOST_PP_SEQ_FOR_EACH_I(MACRO1, ~, seq) Both preprocessors I tried, VC71 and GCC 3.4.2, produce the same result: BOOST_PP_SEQ_FOR_EACH_I(MACRO2, ~, (1)(2)(3) ) BOOST_PP_SEQ_FOR_EACH_I(MACRO2, ~, (4)(5)(6) ) BOOST_PP_SEQ_FOR_EACH_I(MACRO2, ~, (7)(8)(9) ) BOOST_PP_SEQ_FOR_EACH_I_M(3, (MACRO2, ~, (1)(2)(3) (nil), 0)) BOOST_PP_SEQ_FOR_EACH_I_M(4, (MACRO2, ~, (2)(3) (nil), 1)) BOOST_PP_SEQ_FOR_EACH_I_M(5, (MACRO2, ~, (3) (nil), 2)) BOOST_PP_SEQ_FOR_EACH_I_M(4, (MACRO2, ~, (4)(5)(6) (nil), 0)) BOOST_PP_SEQ_FOR_EACH_I_M(5, (MACRO2, ~, (5)(6) (nil), 1)) BOOST_PP_SEQ_FOR_EACH_I_M(6, (MACRO2, ~, (6) (nil), 2)) BOOST_PP_SEQ_FOR_EACH_I_M(5, (MACRO2, ~, (7)(8)(9) (nil), 0)) BOOST_PP_SEQ_FOR_EACH_I_M(6, (MACRO2, ~, (8)(9) (nil), 1)) BOOST_PP_SEQ_FOR_EACH_I_M(7, (MACRO2, ~, (9) (nil), 2)) Which, I think, indicates that reentrancy is not working. Am I missing something? Regards, Arkadiy