virtual functions in ada95

["Thomas Nebel" <thomas_nebel@gmx.de>]

Hi

How can i use virtual functions in Ada? I have a superclass and some classes
that are derived
from it:

type TNTGL_Custom_Node_Record is tagged null record;
type TNTGL_Node_Record is new TNTGL_Custom_Node_Record with private;
type TNTGL_Visual_Node_Record is new TNTGL_Node_Record with private;
type TNTGL_Sphere_Record is new TNTGL_Visual_Node_Record with private;

type TNTGL_Node is access all TNTGL_Node_Record'Class;
type TNTGL_Sphere is access all TNTGL_Sphere_Record'Class;
....
procedure Run (Node : access TNTGL_Node_Record'Class);
procedure Run (Node : access TNTGL_Group_Node_Record'Class);
procedure Run (Sphere : access TNTGL_Sphere_Record'Class);

Now i want to "run" the classes from one point transparently :

Node : TNTGL_Node;
...
Node := Scene.First_Node;
while Node /= null loop
    Run (Node);
    Node := Get_Next (Node);
end loop;

Independent of the real type of the Node variable, the Run function is
always the Run from
TNTGL_Node_Record.

How can i manage it, that the Run function for the real Node type is called
?

Thomas