Re: Type in allocator has deeper level than designated class-wide type

[Adrian Hoe <abyhoe@gmail.com>]

On Jun 14, 1:11 am, Adam Beneschan <a...@irvine.com> wrote:
> On Jun 13, 8:31 am, Adrian Hoe <aby...@gmail.com> wrote:
>
>
>
>
>
> > Hi all,
>
> > I have stomped into above error and I am stuck with the error and
> > runtime exception PROGRAM_ERROR : accessibility check failed.
>
> > Here's the fragment of my codes:
>
> > generic
> >    N : Positive;
> >    type Item is private;
> > package High_Cloud is
>
> >    package List renames Heterogeneous_Doubly_Link_List;
> >    use List;
>
> >    type Data_Array               is array ( 1 .. N ) of Item;
>
> >    type Element_Record           is new List.Node with private;
> >    type Series_Access            is new List.Access_List;
>
> > private
>
> >    type Element_Record is new List.Node with
> >       record
> >          Name           : Unbounded_String;
> >          Color          : Unbounded_String;
> >          Data           : Data_Array;
> >       end record;
>
> > ...
> > end High_Cloud;
>
> > In the package body of High_Cloud, I have a procedure:
>
> >    procedure Add
> >       ( Cloud          : in out High_Cloud_Record;
> >         Name            : in     Unbounded_String;
> >         Color           : in     Unbounded_String;
> >         Data            : in     Data_Array )
> >    is
>
> >       New_Element : List.Access_Node;
>
> >    begin
>
> >       New_Element := new Element_Record'
> > <========== Error/Warning here.
> >                         ( Constructor.Init ( Name, Color, Data) ) ;
>
> >       Concatenate ( Cloud.Series, New_Element ) ;
>
> >    end Add;
>
> > My intention is to use genericity to create a data which is an array
> > (1..N) of any_type. This data is then stored in a list. Procedure Add
> > instantiate (by calling to Constructor.Init) the list's node with
> > data.
>
> > I have read the ARM 3.10.2 and 3.10.1 and also John Barnes book yet I
> > still have no clue how to solve the problem.
>
> > Can you please help? Thanks.
>
> I think we need to see the definition of Constructor.Init, at least.
> (I'm guessing that Heterogeneous_Doubly_Link_List is a library package
> that defines Node as a tagged record and Access_Node as "access all
> Node'Class".  But I don't have a guess about what Init is.)
>
>                                -- Adam


Yes, you are right. In Heterogeneous_Doubly_Link_List:


   type List        is limited private;
   type Access_List is access List;

   type Node           is tagged private;
   type Access_Node   is access all Node'Class;


private

   type Node is tagged record
      Previous : Access_Node;
      Next     : Access_Node;
   end record;

   type List is limited record
      Head    : Access_Node := null;
      Tail    : Access_Node := null;
      Current : Access_Node := null;
      Count   : Unsigned := 0;
   end record;


And:


   package body Constructor is

      function Init
         ( New_Name  : Unbounded_String;
           New_Color : Unbounded_String;
           New_Data  : Data_Array )
      return Element_Record is
      begin
         return ( List.Constructor.Init
                     with
                        Name  => New_Name,
                        Color => New_Color,
                        Data  => New_Data
                ) ;
      end Init;

   end Constructor;

Is the problem lying in the Data : Data_Array in Element_Record or in
the return statement of Constructor.Init?