...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::otherwise —
Syntactic sugar for proto::when< proto::_, Fun >
,
for use in grammars to handle all the cases not yet handled.
// In header: <boost/proto/transform/when.hpp> template<typename Fun> struct otherwise : proto::when< proto::_, Fun > { };
Use proto::otherwise<T>
in your grammars as a synonym for
proto::when< proto::_, Fun >
as in the following transform which counts the number of terminals in an expression.
// Count the terminals in an expression tree. // Must be invoked with initial state == mpl::int_<0>(). struct CountLeaves : proto::or_< proto::when<proto::terminal<proto::_>, mpl::next<proto::_state>()>, proto::otherwise<proto::fold<proto::_, proto::_state, CountLeaves> > > {};