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Struct template _env_var

boost::proto::_env_var — A primitive transform that returns the value associated with a particular Key in the current transform environment.


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

template<typename Key> 
struct _env_var :  proto::transform<_env_var<Key> > {
  // member classes/structs/unions
  struct impl :  proto::transform_impl<Expr, State, Data> > {
    // types
    typedef typename proto::result_of::env_var<Data, Key>::type result_type;

    // public member functions
    result_type operator()(typename impl::expr_param, 
                           typename impl::state_param, 
                           typename impl::data_param) const;


See proto::_env_var::impl for the full details.