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boost::proto::functional::env_var — A unary PolymorphicFunctionObject used for fetching the value associated with a particular key in a transform environment.
// In header: <boost/proto/transform/env.hpp> template<typename Key> struct env_var : proto::callable { // member classes/structs/unions template<typename Sig> struct result { // types typedefsee-belowtype; }; // public member functions template<typename Env>see-belowoperator()(Env const &) const; };
env_var public member functionstemplate<typename Env> see-below operator()(Env const & e) const;
This function behaves as follows:
Key is proto::data_type:
proto::is_env<Env>::value is true,
return e[proto::data].
e.
e[Key()].
See proto::env::operator[] for additional information.