如何为向量创建整数的散列映射？

Question

我正在学习Ada(通过尝试https://adventofcode.com/2018/问题).

我有一个向量ActivityVector的ActivityRecord记录:

type ActivityRecord is 
record
   dt: Ada.Calendar.Time;
   str: UStr.Unbounded_String;
end record;

package ActivityVector is new Ada.Containers.Vectors
   (Element_Type => ActivityRecord,
   Index_Type => Natural);

我想把它们放在键盘的地图上Integer.我有以下内容:

function IntegerHash(i: Integer) return Ada.Containers.Hash_Type;

package ActivityMap is new Ada.Containers.Indefinite_Hashed_Maps(
   Key_Type => Integer,
   Element_Type => Activity.ActivityVector.Vector,
   Hash => IntegerHash,
   Equivalent_Keys => "="
);

当我尝试编译时,我得到:

act_map.ads:9:04: instantiation error at a-cihama.ads:46
act_map.ads:9:04: no visible subprogram matches the specification for "="
act_map.ads:9:04: instantiation error at a-cihama.ads:46
act_map.ads:9:04: default "=" on "Vector" is not directly visible

看起来它期望为向量定义一个相等运算符？我可以定义一个,但首先我想检查一下:

• 我的想法是正确的
• 如果有更简单的方法来实现它

Answer 1

看起来它期望为向量定义一个相等运算符

是.

我可以定义一个

不要这样做,只需使用实例化中定义的现有函数Ada.Containers.Vectors:

package ActivityMap is new Ada.Containers.Indefinite_Hashed_Maps(
   Key_Type => Integer,
   Element_Type => Activity.ActivityVector.Vector,
   Hash => IntegerHash,
   Equivalent_Keys => "=",
   "=" => Activity.ActivityVector."="
);

或者,Activity.ActivityVector."="通过执行直接使功能可见

use type Activity.ActivityVector.Vector;