Ada中对象的Synchronous_Fifo

Question

我在Ada中创建了记录，后来又从这些记录中创建了Synchronous_Fifo：

type Basic_Record is record
  Argument_1: Integer;
  Operator: Character;
  Argument_2: Integer;
  Product: Integer;
end record;

package Tasks_Fifo is new Synchronous_Fifo(Basic_Record);
use Tasks_Fifo;
Buffer : Fifo;

而且这个运行得很好。后来，我想在对象之外做同样的Synchronous_Fifo：

package Adding_Machine is
  protected type Add_Machine is
     entry Store_Record(Task_Record: Basic_Record);
     entry Push_Button;
     entry Get_Product(Product: out Integer);
  private
     My_Record : Basic_Record;
     My_Product: Integer;
  end Add_Machine;
end Adding_Machine;

use Adding_Machine;

package Object_Fifo is new Synchronous_Fifo(Add_Machine);
use Object_Fifo;
Buffer: Fifo;

结果我得到了几个错误：

Multiple markers at this line
- Occurrence of package
- actual for non-limited "Element_Type" cannot be a limited type
- instantiation abandoned

在队列中，我在这里创建Object_Fifo。

我应该如何创建这个Fifo？或者可能是Adding_Machine包出了问题

Answer 1

下面显示的是package Synchronous_Fifo

generic
     type Element_Type is private;
package Synchronous_Fifo is
  protected type Fifo is
    entry Push(Item : Element_Type);
    entry Pop(Item : out Element_Type);
  private
    Value : Element_Type;
    Is_New : Boolean := False;
  end Fifo;
end Synchronous_Fifo;

package body Synchronous_Fifo is

 ----------
 -- Fifo --
 ----------

 protected body Fifo is

  ---------
  -- Push --
  ---------

  entry Push (Item : Element_Type) when not Is_New is
  begin
     Value := Item;
     Is_New := True;
  end Push;

  ---------
  -- Pop --
  ---------

  entry Pop (Item : out Element_Type) when Is_New is
  begin
     Item := Value;
     Is_New := False;
  end Pop;

 end Fifo;

end Synchronous_Fifo;

我创建了对Adding_Machine的访问，后来又通过这些访问创建了先进先出。

type Adding_Machine_Access is access Adding_Machine;

package Adding_Machines_Fifo is new Synchronous_Fifo(adding_Machine_Access);
use Tasks_Fifo;
Adding_Machines_Fifo : Fifo;

应该能行得通。