--|  
--| Filename        : $Source: /home/erdmann/ASCL/Template/RCS/template.ads,v $
--| Description     : Template Specification
--| Author          : Michael Erdmann
--| Created On      : 25.3.1999
--| Last Modified By: $Author: erdmann $
--| Last Modified On: $Date: 1999/08/01 10:57:25 $
--| Status          : $State: Exp $
--|
--|
--| Functional Description
--| ======================
--|
--|
--| Component Data
--| ==============
--|
--| Every component is based upon an data type. The data type
--| is allwyas called "Object". This name is choosen fixed in 
--| oder to make the namin as simple as possible, because sometimes
--| you will find redundant naming i.e. List.List_Type.
--|
--| Every Basic class will export a class wide pointer called
--| Handle.
--|
--| The Object is self hides completly the implementation of the 
--| data structure because it is simply a reference to the 
--| actual Object_data. 
--|
--| The lifecyle of an instance is alway between an Initialize
--| an a Finalize call.
--|
--| Operations on the component data
--| ================================
--| There are two basic types of operations assuemed. So called
--| attribute functions and methods.
--|
--| Attribute functions are used to set and get data items. They
--| do not change any internal state of the component. Please keep
--| in mind, that a state is persisten over the life time of the 
--| instance. This methods allows the seperate the implmentation
--| of data kept in the component from the outside representation.
--|  
--| A method changes the internal state of the component (i.e
--| a file pointer) and may pass data to or return data from
--| the component.
--|
--| Error Handling
--| ==============
--| Design by contract should be applied, this means input parameter
--| are not checked, the caller has to ensure the correct usage.
--| The component has only to ensure some kind of fiendly behaiviour 
--| by raising an exception.
--|
--| Raising exceptions should always be prefered over return codes
--| indicating a problem.
--|
--| Any how the following exceptions can be raised by any component:
--|
--| Not_Initialized  - The object passed to the component was never
--|                    initialized.
--| Usage_Error      - Some kind of handling error regarding the 
--|                    use case hase been done, i.e. read used 
--|                    before file opend.
--|
--| Out_of_Memory    - We tried to initialize and instance, but the 
--|                    object could not be created because no memory
--|                    is available any more.
--|
--|
--| Extension
--| =========
--| If the object is abstract normaly the class requires some 
--| extentsion to implemented.
--|
--| Restrictions
--| ============
--| Tasking: yes/no
--| Y2K    :
--|
--|
--| History
--| =======
--| $Log: template.ads,v $
--| Revision 1.2  1999/08/01 10:57:25  erdmann
--| Debugging support added and compiled
--|
--| Revision 1.1  1999/07/18 15:35:08  erdmann
--| No comments
--|
--|

with ASCL.Debugging_Support;

use  ASCL;

package Template is
   
   ---=====================================================================---
   ---===             C O M P O N E N T   I N T E R F A C E             ===---
   ---=====================================================================---
   type Object is abstract tagged private;
   type Handle is access Object'Class;

   procedure Initialize( this  : in out Object'Class;
                         debug : in Debugging_Support.Handle := null );

   procedure Finalize( this : in out Object'Class );

   ---=====================================================================---
   ---===                  A T T R I B U T E S                       ===---
   ---=====================================================================---

   procedure Set( this : in out Object'Class; value : in Integer );
   function  Get( this : in Object'Class ) return Integer;

   ---=====================================================================---
   ---===                     M E T H O D S                             ===---
   ---=====================================================================---

   ---------------------------------------------------------------------------
   --| Description    :
   --| Preconditions  :
   --| Postconditions :
   --| Exceptions     :
   --| Note           :
   ---------------------------------------------------------------------------
   procedure Perform( this : in out Object'Class );

   ---=====================================================================---
   ---===                   E X T E N S I O N                           ===---
   ---=====================================================================---
   procedure Initialize( this : in out Object )                    is abstract;
   procedure Finalize( this : in out Object )                      is abstract;

   ---=====================================================================---
private
   type Object_Data;
   type Object_Data_Access is access Object_Data;

   type Object is abstract tagged record
         data : Object_Data_Access := null;
      end record; 

end Template;