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Struct template is_env

boost::proto::is_env — A Boolean metafuntion for determining whether or not a type is a Proto transform environment.


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

template<typename T> 
struct is_env :  mpl::bool_<true-or-false> {


is_env<T> inherits from mpl::true_ under the following conditions:

  • If T is proto::empty_env.
  • If T is a specialization of proto::env<>.
  • If T is derived from any of the above.
  • If T is a cv-qualified variant of any of the above.
  • If T is a reference to any of the above.

Otherwise, is_env<T> inherits from mpl::false_.