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          attribute_as atomically
          extracts an instance of a type from another type. This customization point
          is used by the as<T>[]
          directive.
        
#include <boost/spirit/home/support/attributes_fwd.hpp>
Also, see Include Structure.
| ![[Note]](../../../images/note.png) | Note | 
|---|---|
| This header file does not need to be included directly by any user program as it is normally included by other Spirit header files relying on its content. | 
| Name | 
|---|
| 
                     | 
template <typename T, typename Attribute, typename Enable = void> struct attribute_as;
| Parameter | Description | Default | 
|---|---|---|
| 
                     | 
                    The type of the attribute natively exposed by the component the
                     | none | 
| 
                     | The type of the attribute to be used to generate output from. | none | 
| 
                     | 
                    Helper template parameter usable to selectively enable or disable
                    certain specializations of  | 
                     | 
Notation
attr
                An instance of type Attrib.
              
| Expression | Semantics | 
|---|---|
| 
                     | The result type of the extraction. | 
| 
                     | 
                    Extract and return an instance of  | 
| 
                     | 
                    Determine, at runtime, if the extraction of an instance of  | 
Spirit predefines specializations of this customization point for several types. The following table lists those types together with the types exposed and the corresponding semantics:
| Template Parameters | Semantics | 
|---|---|
| 
                     | 
                    The exposed typedef  | 
          This customization point may need to be implemented when using the as<T>[] directive.