Ada 编译器放弃通过重载运算符的包实例化

Question

我想实例化一个包并将重载运算符的函数传递给它，以便制作通用二叉搜索树。这是规格。

bstgen.ads（片段）

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Unchecked_Deallocation;

GENERIC
   type Akey is private;
   type TreeRecord is private;
   with function "<"(K: in Akey; R: in TreeRecord) return Boolean;
   with function ">"(K: in Akey; R: in TreeRecord) return Boolean;
   with function "="(K: in Akey; R: in TreeRecord) return Boolean;

PACKAGE BSTGen IS

   TYPE St10 IS NEW String(1..10);
   TYPE TreePt IS PRIVATE;
   PACKAGE EnumIO IS NEW Ada.Text_IO.Enumeration_IO(Akey); USE EnumIO;

driver.adb（片段）

with Ada.Text_IO; use Ada.Text_IO;
WITH BSTGen;

PROCEDURE Driver IS
   IP: Integer := 1;
   TYPE Names IS (Resig,Keene,Marsden,Vuijic,Marcus,Gonzalez);
   PACKAGE NamesIO IS NEW Ada.Text_IO.Enumeration_IO(Names);
   type St10 is NEW String(1..10);
   type Customer is 
      record Name:  Names;  
      PhoneNumber: St10; 
   end record;
   function "<"(K: in Names; R: in Customer) return Boolean is begin
      return K < R.Name;
   end "<";
   function ">"(K: in Names; R: in Customer) return Boolean is begin
      return K > R.Name;
   end ">";
   function "="(K: in Names; R: in Customer) return Boolean is begin
      return K = R.Name;
   end "=";
   PACKAGE IntIO IS NEW Ada.Text_IO.Integer_IO(Integer); USE IntIO;
   PACKAGE mybst is NEW BSTGen(Names,Customer,<,>,=); USE mybst;
   R, Pt: TreePt;
   Name: Names;
   Phone: St10;
   Status: Boolean;
BEGIN
   R := CreateTree;
   Pt := R;

然而，当我尝试编译时，这是输出：

driver.adb:24:04: expect subprogram or entry name in instantiation of "<"
driver.adb:24:04: instantiation abandoned
bstgen.ads:19:53: expect discrete type in instantiation of "Enum"
bstgen.ads:19:53: instantiation abandoned

这包括一堆错误，指出 driver.adb 的方法不可见，这是预期的，因为 mybst 的实例化被放弃了。我该如何解决这个问题？

Answer 1

在bstgen.ads，你说

PACKAGE EnumIO IS NEW Ada.Text_IO.Enumeration_IO(Akey);

但你说的是通用形式部分

type Akey is private;

这意味着除了相等和赋值可用之外，编译器对实际类型的假设很少。它可能是数百字节的记录；它当然不需要是一个枚举。

要保证Akey是一个枚举，需要说

type Akey is (<>);

如 ARM12.5(13)。

在driver.adb，你说

PACKAGE mybst is NEW BSTGen(Names,Customer,<,>,=);

应该读作

PACKAGE mybst is NEW BSTGen(Names,Customer,”<“,”>”,”=“);

Ada 编译器放弃通过重载运算符的包实例化

Ada Compiler abandons Instantiation of package passing overloaded operators

operator-overloading

instantiation

ada