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From: el97165@central.ntua.gr (moasi)
Newsgroups: comp.lang.ada
Subject: Polymorfism Question
Date: 19 Aug 2000 00:12:07 GMT
Organization: National Technical University of Athens
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I have a linked list. And i have done several classes and subclasses.
So i create objects of different classes and make a heterogeneous list.
Now i want to print the list. Each element in list has different
fields, so when i ask for the list i don't get all the fields
but just the basics. How can i alter that?
Here is my program:

procedure Print_All_Obligations(MyList: access List) is

        Current_Ptr : Obligation_Ptr;
        CheckMyList : Integer_Check;

  begin
    Reset_Cursor(MyList);
    Current_Ptr := Obligation_Ptr(Return_Cursor(MyList));
    if Current_Ptr /= null then
    begin
      Print(Current_Ptr);
      loop
        CheckMyList := Go_Next_Element(MyList);
        exit when CheckMyList /= 0;
        New_Line;
        Current_Ptr := Obligation_Ptr(Return_Cursor(MyList));
        Print(Current_Ptr);
      end loop;
    end;
    else Put_Line ("--> Nothing In List!");
    end if;
   New_Line;
end Print_All_Obligations;

The classes starting for the top are:
element --> obligation --> meeting --> b_meeting and p_meeting 
the last 2 are in the same level (they both have meeting as their parent).
All classes except the element have a print, and when i call
the print of b_meeting, it prints something then calls the print
of meeting and the print of meeting calls the print of obligation.
I have also declared pointers for each class like that
type Element_Ptr is access all Element'Class;
                            
In general how can i understand each time in what kind of
element am i so that i can print the correct fields?

Please feel free to give any hints, remarks or advices!

-- 
Antonis Zisimos