Struct template left

boost::proto::result_of::left — A metafunction that returns the type of the left child of a binary Proto expression.

Synopsis

// In header: <boost/proto/traits.hpp>

template<typename Expr> 
struct left :  proto::result_of::child_c< Expr, 0 > {
};

proto::result_of::left<Expr> is equivalent to proto::result_of::child_c<Expr, 0>.