tool::static_base< Bottom > Struct Template Reference

Base class of all static hierachies. More...

#include <wipal/tool/static_base.hh>

List of all members.

Public Types

typedef HIDDEN exact_type

Public Member Functions

Downcast methods
const exact_typeexact () const
exact_typeexact ()
const exact_typeexact_ptr () const
exact_typeexact_ptr ()


Detailed Description

template<class Bottom>
struct tool::static_base< Bottom >

Base class of all static hierachies.

A static hierarchy is a class hierarchy within which each class knows its exact type thanks to specific template parameters.

E.g.

   static_base<cow> : animal<cow> : mammal<cow> : cow

static_base's main role is to provide the exact() and exact_ptr() methods. These methods allow intermediate classes in the hierarchy to static_cast themselves directly to their exact type. This is perfectly type safe.

E.g.

   template <class Exact>
   void
   animal<Exact>::eat()
   {
     this->exact().eat_impl(); // Delegate eat() to Exact::eat_impl().
   }

In the previous example however, one cannot subclass cow because it has no Exact parametter. Use the bottom class to solve this issue:

   static_base<cow<bottom>> : animal<cow<bottom>> : mammal<cow<bottom>> :
     cow<bottom>

     or

   static_base<highland_cow<bottom>> : animal<highland_cow<bottom>> :
     mammal<highland_cow<bottom>> : cow<highland_cow<bottom>> :
     highland_cow<bottom>

In this example however, cow must provide to mammal either highland_cow<bottom> either cow<bottom>, depending on its template parameter. This is done using the get_exact trait:

   template <class Bottom>
   struct cow:
     public mammal<typename get_exact< Bottom, cow<Bottom> >::return_type>
   {
     // Inherit mammal<cow<bottom>> if Bottom = bottom,
     // inherit mammal<Bottom>, else.

     // ...
   };

For simple cases, we provide the WP_GET_EXACT() and WP_INHERIT() preprocessor macros:

   template <class Bottom>
   struct cow: WP_INHERIT(public mammal, cow<Bottom>)
   {
     typedef WP_GET_EXACT(Bottom, cow<Bottom>) exact_type;

     // ...
   };

Member Typedef Documentation

template<class Bottom>
typedef HIDDEN tool::static_base< Bottom >::exact_type


Member Function Documentation

template<class Bottom >
static_base< Bottom >::exact_type & tool::static_base< Bottom >::exact (  )  [inline]

Safely downcast to the exact type as a non-const reference.

template<class Bottom >
const static_base< Bottom >::exact_type & tool::static_base< Bottom >::exact (  )  const [inline]

Safely downcast to the exact type as a const reference.

template<class Bottom >
static_base< Bottom >::exact_type * tool::static_base< Bottom >::exact_ptr (  )  [inline]

Safely downcast to the exact type as a non-const pointer.

template<class Bottom >
const static_base< Bottom >::exact_type * tool::static_base< Bottom >::exact_ptr (  )  const [inline]

Safely downcast to the exact type as a const pointer.


The documentation for this struct was generated from the following files:

Generated on Wed Apr 22 22:52:43 2009 for wipal by  doxygen 1.5.8