Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Struct template is_env

Struct template is_env

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

Synopsis

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

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

Description

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_.