Re: virtual functions in ada95

[tmoran@acm.org]

>How can i use virtual functions in Ada?
  "An Ada dispatching subprogram is analogous to a C++ virtual function."
p 27, Ada as a Second Language, ISBN 0-07-011607-5

> 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;

> procedure Run (Node : access TNTGL_Node_Record'Class);
> procedure Run (Sphere : access TNTGL_Sphere_Record'Class);

  A TNTGL_Sphere_Record, or any descendant of one, is also a descendant of
TNTL_Node_Record.  Which Run would you like to call in that case?
I think you want to drop the 'Class from the Run procedure declarations,
and have Run dispatch based on the run-time type of its paramter.

  procedure Run (Node : access TNTGL_Node_Record);
  procedure Run (Sphere : access TNTGL_Sphere_Record);
anything from a TNTGL_Node_Record up to the parent of a
TNTGL_Sphere_Record would call the first Run, a Sphere or its
descendants would call the second Run.