...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::result_of::child — A metafunction that returns the type of the N
th
child of a Proto expression, where N is an MPL Integral Constant.
// In header: <boost/proto/traits.hpp> template<typename Expr, typename N = mpl::long_<0> > struct child : proto::result_of::child_c<Expr, N::value> { };
proto::result_of::child<Expr, N>
is equivalent to
proto::result_of::child_c<Expr, N::value>
.