Boost C++ Libraries Home Libraries People FAQ More

PrevUpHomeNext

Struct template impl

boost::proto::when<Grammar, >::impl

Synopsis

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


template<typename Expr, typename State, typename Data> 
struct impl :  
    proto::result_of::has_env_var<proto::transforms_type>::proto::result_of::env_var<proto::transforms_type>,
        proto::result_of::env_var<proto::data_type>
      >::
{
};

Description

The implementation of the impl struct depends on whether the Data parameter is a transform environment that contains a value corresponding to the proto::transforms_type key. If so, that value is treated as a map from rules to transforms. Otherwise, the Data type itself is treated as such a map.


PrevUpHomeNext