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
#
#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
