...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::not_ — Inverts the set of expressions matched by a grammar. When used as a transform,
proto::not_<>
returns the current expression unchanged.
// In header: <boost/proto/matches.hpp> template<typename Grammar> struct not_ : proto::transform<not_<Grammar> > { // types typedef not_ proto_grammar; // member classes/structs/unions template<typename Expr, typename State, typename Data> struct impl : proto::transform_impl<Expr, State, Data> { // types typedef Expr result_type; // public member functions Expr operator()(typename impl::expr_param, typename impl::state_param, typename impl::data_param) const; }; };
If an expression type E
does not match a grammar
G
, then E
does
match proto::not_<G>
. For example,
proto::not_<proto::terminal<proto::_> >
will match any non-terminal.