My bug or else regarding Visibility Rules

[Anh Vo <anhvofrcaus@gmail.com>]

For the codes below GNAT complains that In_Index, Buffer, and Out_Index are undefined. However, if I comment out private key word, GNAT is happy. Did I violate Ada syntax rules? Thanks.


generic
   type Element is private;
   Length : Positive := 1;

package Circular_Queue is

   -- Indicates incorrect usage
   Queue_Error : Exception;

   -- Places an item in the queue.
   procedure Put (Item : Element)
     with pre => not Queue_Full,
          Post => (In_Index = In_Index'Old mod Length + 1) and
                  (Buffer(In_Index'Old) = Item) and 
                  (for all I in 1 .. Queue_Length'Old =>
                                Buffer(I) = Buffer'Old (I)) and 
                  (not Queue_Empty);
  
   -- Takes an item from the queue.
   function Get return Element
      with pre => not Queue_Empty,
           Post => (Out_Index = Out_Index'Old mod Length + 1) and
                   (Buffer(Out_Index'Old) = Get'Result) and 
                   (for all I in 1 .. Queue_Length =>
                                 Buffer(I) = Buffer'Old (I)) and 
                   (not Queue_Full);

   -- Returns the depth of the queue
   function Queue_Length return Natural;

   -- Indicates if the queue is full or not
   function Queue_Full return Boolean;

   -- Indicates if the queue is empty or not
   function Queue_Empty return Boolean;

private
   subtype Index is Positive range 1 .. Length;
   type Element_Array is array (Index) of Element;

   Buffer : Element_Array;
   In_Index : Index := 1;
   Out_Index : Index := 1;
   Count: Natural range 0 .. Length := 0;
end Circular_Queue;