Hello all, I have a curiosity about Boost.Preprocessor: What is the difference between pp-lists and pp-sequences starting with a NIL element? PP-Lists can be empty or nil (e.g., have 0 size, etc) while pp-sequences cannot. However, I could use sequences that always start with a nil element `(NIL) ...` and write macros that ignore this 1st element so to handle empty pp-sequences: #define NILSEQ_SIZE(nilseq) BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(nilseq)) NILSEQ_SIZE( (NIL) ) // 0 NILSEQ_SIZE( (NIL)(a) ) // 1 NILSEQ_SIZE( (NIL)(a)(b) ) // 2 BOOST_PP_LIST_SIZE( BOOST_PP_NIL ) // 0 BOOST_PP_LIST_SIZE( (a, BOOST_PP_NIL) ) // 1 BOOST_PP_LIST_SIZE( (a, (b, BOOST_PP_NIL)) ) // 1 Similarly, I could program NILSEQ_FOR_EACH, NILSEQ_ENUM, etc. What are the pros and cons of using pp-nil-sequences vs pp-lists given that both allow for emptiness? Thank you very much. -- Lorenzo