Hello, I'd like to thank everybody involved in creation of Boost.Preprocessor for this cool piece of software, it does wonders. I have a possibly naive question (I'm an autodidact) which involves Boost.PP. I have stumbled upon strange behavior where the preprocessor stops expanding but the output expands further if fed to the preprocessor again. Given these directives: #include <boost/preprocessor.hpp> # #define DAPHP_REGISTER_CLASS(class_, props) \ CXXEXT_REGISTER_CLASS( \ class_ \ , BOOST_PP_SEQ_TRANSFORM(DAPHP_MAKE_PROPERTY, ~, props) \ ) # #define DAPHP_MAKE_PROPERTY(_, __, name) \ (name, IS_LONG, 0) # #define CXXEXT_REGISTER_CLASS(class_, props) \ object< class_ >::register_(); \ CXXEXT_DECLARE_PROPERTIES(class_, props) # #define CXXEXT_DECLARE_PROPERTIES(class_, props) \ BOOST_PP_SEQ_FOR_EACH( \ CXXEXT_DECLARE_PROPERTY_SEQ \ , ~ \ , BOOST_PP_SEQ_TRANSFORM(CXXEXT_PROPERTY_ADD_CLASS, class_, props) \ ) # #define CXXEXT_PROPERTY_ADD_CLASS(_, class_, prop) \ BOOST_PP_ARRAY_DATA(BOOST_PP_ARRAY_PUSH_FRONT((3, prop), class_)) # #define CXXEXT_DECLARE_PROPERTY_SEQ(_, __, elem) \ BOOST_PP_EXPAND(CXXEXT_DECLARE_PROPERTY elem) # #define CXXEXT_DECLARE_PROPERTY(native_type, name, ztype_, default_) \ object< native_type >::declare_property( \ ZEND_ACC_PUBLIC \ , ztype_ \ , BOOST_PP_STRINGIZE(name) \ , default_ \ ); # #define DAPHP_PROPS_DATE (year) (month) (day) This: DAPHP_REGISTER_CLASS(DapiDate, DAPHP_PROPS_DATE) Expands to (newlines added): object< DapiDate >::register_(); object< DapiDate >::declare_property( ZEND_ACC_PUBLIC , IS_LONG , "year" , 0 ); object< DapiDate >::declare_property( ZEND_ACC_PUBLIC , IS_LONG , "month" , 0 ); object< DapiDate >::declare_property( ZEND_ACC_PUBLIC , IS_LONG , "day" , 0 ); With these definitions added to the mix: #define DAPHP_REGISTER_CLASSES(classes) \ BOOST_PP_SEQ_FOR_EACH( \ DAPHP_REGISTER_CLASS_SEQ \ , ~ \ , classes \ ) # #define DAPHP_REGISTER_CLASS_SEQ(_, __, classprops) \ DAPHP_REGISTER_CLASS( \ BOOST_PP_TUPLE_ELEM(2, 0, classprops) \ , BOOST_PP_TUPLE_ELEM(2, 1, classprops) \ ) This: DAPHP_REGISTER_CLASSES( ((DapiDate, DAPHP_PROPS_DATE)) ) Expands to (newlines added): object< DapiDate >::register_(); BOOST_PP_SEQ_FOR_EACH( CXXEXT_DECLARE_PROPERTY_SEQ , ~ , ((DapiDate, year, IS_LONG, 0)) ((DapiDate, month, IS_LONG, 0)) ((DapiDate, day, IS_LONG, 0)) ) Which is an intermediate expansion of the above listed DAPHP_REGISTER_CLASS(DapiDate, DAPHP_PROPS_DATE). g++ 4.5.0 (MinGW) and MSVC 9 Express behave the same, which makes me believe this is a PEBKAC, but I just don't see it. Why doesn't DAPHP_REGISTER_CLASSES expand all the way as DAPHP_REGISTER_CLASS does? Please enlighten me. -- roman