...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::proto::_child_c — A PrimitiveTransform that returns N-th child of the current expression.
// In header: <boost/proto/transform/arg.hpp> template<int N> struct _child_c : proto::transform< _child_c<N> > { // member classes/structs/unions template<typename Expr, typename State, typename Data> struct impl : proto::transform_impl< Expr, State, Data > { // types typedef typename proto::result_of::child_c< Expr, N >::type result_type; // public member functions typename proto::result_of::child_c< Expr, N >::type operator()(typename impl::expr_param, typename impl::state_param, typename impl::data_param) const; }; };
Example:
proto::terminal<int>::type i = {42}; proto::terminal<int>::type & j = proto::_child_c<0>()(-i); assert( boost::addressof(i) == boost::addressof(j) );