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

This is an older version of Boost and was released in 2017. The current version is 1.89.0.

Function has_env_var

Function has_env_var

boost::proto::has_env_var — For testing to see whether a value exists in a transform environment corresponding to the specified Key.

Synopsis

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


template<typename Key, typename Env> 
  typename proto::result_of::has_env_var<Env &, Key>::type 
  has_env_var(Env & e);
template<typename Key, typename Env> 
  typename proto::result_of::has_env_var<Env const &, Key>::type 
  has_env_var(Env const & e);

Description

See also:

proto::functional::has_env_var::operator()

Returns:

proto::functional::has_env_var<Key>()(e)