# include <boost/cstdlib.hpp>
# include <boost/proto/proto.hpp>
# include <boost/fusion/container/list/cons.hpp>

# include <boost/proto/tags.hpp>
# include <boost/proto/make_expr.hpp>

# define PRECISION_MAKE_tag(name)												\
struct name																		\
{																				\
	friend std::ostream& operator<< (std::ostream& s, name const&)				\
	{																			\
	return s<< #name;															\
	}																			\
};

# define PRECISION_MAKE_terminal(name)											\
proto::terminal< tag::name >::type const name = {{}}

namespace proto = boost::proto;

namespace tag{	
	PRECISION_MAKE_tag(a);
	PRECISION_MAKE_tag(b);
	PRECISION_MAKE_tag(c);
}

namespace mpl = boost::mpl;
namespace fusion = boost::fusion;
using proto::_;

#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1500))
#define _left call<proto::_left>
#define _right call<proto::_right>
#define _make_plus(x,y) call<proto::_make_plus(x,y)>
#define _make_multiplies(x,y) call<proto::_make_multiplies(x,y)>
#endif

struct DistributiveLaw :
	proto::or_<
		proto::when<
			proto::multiplies< _, proto::plus< _, _ > >
		  , proto::_make_plus(
				proto::_make_multiplies(
					proto::_left
				  , proto::_left( proto::_right )
				)
			  , proto::_make_multiplies(
					proto::_left
				  , proto::_right( proto::_right )
				)
			)
		>
	>
{};

PRECISION_MAKE_terminal(a);
PRECISION_MAKE_terminal(b);
PRECISION_MAKE_terminal(c);

# undef PRECISION_MAKE_tag
# undef PRECISION_MAKE_terminal

int main()
{
	proto::display_expr(a*(b+c));

	proto::display_expr(DistributiveLaw()( a*(b+c)  ));
	return boost::exit_success;
}