"全视图声明必须出现在私密部分"的说明

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.它抛出了指向该行的错误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)你需要在私人部分提供完整的声明; 当然,这意味着你必须拥有私人部分.

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在包装外面看到,你需要说出类似的话

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;
         ...