[C++] foreach for pure macro, Qt, and boost

foreach.h

/***** macro foreach *****/
#define EASY_FOREACH(it, container) \
	for(typeof((container).begin()) it = (container).begin();it != (container).end(); ++it)

	
/***** qt foreach *****/
template <typename T>
class ForeachContainer {
public:
	inline ForeachContainer(const T& t) : c(t), brk(0), i(c.begin()), e(c.end()) { }
	const T c; // avoid copy op, using reference (const T &c)
	int brk;
	typename T::const_iterator i, e;
};

#define QT_FOREACH(variable, container)							\
for (ForeachContainer<__typeof__(container)> _container_(container)			\
	!_container_.brk && _container_.i != _container_.e				\
	__extension__({ ++_container_.brk; ++_container_.i; })				\
	for (variable = *_container_.i;; __extension__({--_container_.brk; break;}))


/***** boost foreach for pair *****/
#include <boost/foreach.hpp>
#include <boost/tuple/tuple.hpp>

namespace __foreach__ {
// NOTE: This is a copied from Boost
// (boost/tuple/detail/tuple_basic_no_partial_spec.hpp) because the
// new 'boost::tuples::ignore' does not work in our 'foreachkey' and
// 'foreachvalue'.
struct swallow_assign {
	template<typename T>
	swallow_assign const& operator=(const T&) const {
		return *this;
	}
};

swallow_assign const ignore = swallow_assign();
} /* namespace __foreach__ */

#define BOOST_FOREACH_PAIR(VARFIRST, VARSECOND, COL)									\
	BOOST_FOREACH_PREAMBLE()											\
	if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_col) = BOOST_FOREACH_CONTAIN(COL)) {} else	\
	if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_cur) = BOOST_FOREACH_BEGIN(COL)) {} else	\
	if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_end) = BOOST_FOREACH_END(COL)) {} else		\
	for (bool BOOST_FOREACH_ID(_foreach_continue) = true, BOOST_FOREACH_ID(_foreach_onetime) = true;		\
			  BOOST_FOREACH_ID(_foreach_continue) && !BOOST_FOREACH_DONE(COL);				\
			  BOOST_FOREACH_ID(_foreach_continue) ? BOOST_FOREACH_NEXT(COL) : (void)0)			\
		if (boost::foreach_detail_::set_false(BOOST_FOREACH_ID(_foreach_onetime))) {} else			\
		for (VARFIRST = BOOST_FOREACH_DEREF(COL).first;								\
			 !BOOST_FOREACH_ID(_foreach_onetime);								\
			 BOOST_FOREACH_ID(_foreach_onetime) = true)							\
			if (boost::foreach_detail_::set_false(BOOST_FOREACH_ID(_foreach_continue))) {} else		\
			for (VARSECOND = BOOST_FOREACH_DEREF(COL).second;						\
				 !BOOST_FOREACH_ID(_foreach_continue);							\
				 BOOST_FOREACH_ID(_foreach_continue) = true)
				 
#define FOREACH BOOST_FOREACH
#define FOREACH_PAIR BOOST_FOREACH_PAIR

#define FOREACH_KEY(VAR, COL) \
	FOREACH_PAIR (VAR, __foreach__::ignore, COL)

#define FOREACH_VALUE(VAR, COL) \
	FOREACH_PAIR (__foreach__::ignore, VAR, COL)