Ada Compiler放弃了传递重载运算符的包的实例化

Question

我想实例化一个包并将函数传递给它重载运算符,以便创建一个通用二进制搜索树.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;

但是,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的方法是不可见的,这是因为mybst的实例化被放弃所预期的.我该如何解决？

Answer 1

在bstgen.ads,你说

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

但在你说的通用正式部分

type Akey is private;

这意味着编译器可以对实际类型假设很少,除了相等和赋值可用.它可能是数百字节的记录; 它当然不一定是枚举.

要确保这Akey是枚举,您需要说

type Akey is (<>);

与ARM12.5(13)中一样.

在driver.adb,你说

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

哪个应该读

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