compiler-errors - "Declaration of full view must appear in private part"的解释

Question

我收到一个错误，我找不到任何文档来解释我的代码中需要修复的内容。代码是:

   type BinarySearchTreePoint is limited private;
   type Node;
   type BinarySearchTreePoint is access Node;

   type Node is
      record
         Llink, Rlink : BinarySearchTreePoint;
         Ltag, Rtag : Boolean; --True indicates pointer to lower level,
                               -- False a thread.
         Info : Customer;
      end record;

我得到的错误是 declaration of full view must appear in private part .它抛出这个错误指向行 type BinarySearchTreePoint is access Node; ，我不确定错误消息的含义。

Answer 1

当你说 type Foo is private; (或 limited private )您需要在私有(private)部分提供完整的声明；当然，这意味着您必须拥有私有(private)部分。

您显示的代码将编译

package Foo is
   type BinarySearchTreePoint is limited private;
private
   type Node;
   type BinarySearchTreePoint is access Node;

   type Node is
      record
         Llink, Rlink : BinarySearchTreePoint;
         ...

但如果你需要 Node要在包裹外可见，您需要说类似的话

package Foo is
   type BinarySearchTreePoint is limited private;
   type Node is private;
   --  stuff to do with getting a Node from a BinarySearchTreePoint??
   function Content (Of_Node : Node) return Customer;
private
   type BinarySearchTreePoint is access Node;

   type Node is
      record
         Llink, Rlink : BinarySearchTreePoint;
         ...