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 2019. The current version is 1.89.0.

Struct as_env

Struct as_env

boost::proto::functional::as_env — A unary PolymorphicFunctionObject for ensuring that an object is a transform environment. If it isn't already, it is turned into one such that the object is associated with the proto::data_type key.

Synopsis

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


struct as_env :  proto::callable {
  // member classes/structs/unions
  template<typename Sig> 
  struct result {
    // types
    typedef see-below type;
  };

  // public member functions
  template<typename T> see-below operator()(T &) const;
  template<typename T> see-below operator()(T const &) const;
};

Description

`as_env` public member functions

```
template<typename T> see-below operator()(T & t) const;
template<typename T> see-below operator()(T const & t) const;
```
If proto::is_env<T>::value is false, this function returns the result of (proto::data = t). See proto::data_type::operator= for details.

Otherwise, this function returns t by reference.