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Struct _expr

boost::proto::_expr — A PrimitiveTransform that returns the current expression unmodified.


// In header: <boost/proto/transform/arg.hpp>

struct _expr :  proto::transform< _expr > {
  // 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;



proto::terminal<int>::type i = {42};
proto::terminal<int>::type & j = proto::_expr()(i);
assert( boost::addressof(i) == boost::addressof(j) );