Re: [Boost-users] [preprocessor] Strange BOOST_PP_CAT behavior

Sergey wrote:

I can't understand problem with code like this:

#define SOME_SEQ (1)(2)(3) #define BAR_MACRO_1(S) BOOST_PP_SEQ_ENUM(BOOST_PP_SEQ_TAIL(S)) #define FOO_MACRO(S) BOOST_PP_CAT(BAR_MACRO_, BOOST_PP_SEQ_HEAD(S) ##

(S)) ^ Are you missing a 1?

FOO_MACRO(SOME_SEQ)

After preprocessing it looks like BOOST_PP_CAT(BOOST_PP_SEQ_ENUM_, BOOST_PP_CAT(BOOST_PP_SEQ_SIZE_, BOOST_PP_SEQ_SIZE_2)) (2)(3)

If I replace BOOST_PP_CAT with my own macro:

#define MY_CAT(a, b) MY_CAT_I(a, b) #define MY_CAT_I(a, b) a ## b

Everything is all right after preprocessing: 2, 3

Why? What is wrong?

-- Best Regards, Sergey mailto:flex_ferrum@artberg.ru