使用范围作为其索引的数组的索引类型是什么?

解决方案是,匿名整数范围始终成为 Integer 亚型:

with Ada.Text_IO;

procedure Range_Of_Universal_Integer is

   type A is array (1 .. 10) of Integer;

   generic
      type Length_T is range <>;
      type Index_T is (<>);
      type Element_T is limited private;
      type Array_T is array (Index_T) of Element_T;
   function List_Image (Length : in Length_T;
                        Items  : in Array_T) return String;

   function List_Image (Length : in Length_T;
                        Items  : in Array_T) return String is
      pragma Unreferenced (Length, Items);
   begin
      return "Hello";
   end List_Image;

   subtype A_Lengths is Integer range 0 .. A'Length;
   subtype A_Range   is Integer range A'Range;

   function Image is
     new List_Image (Length_T  => A_Lengths,
                     Index_T   => A_Range,
                     Element_T => Integer,
                     Array_T   => A);

begin
   Ada.Text_IO.Put_Line (Image (Length => 0,
                                Items  => A'(others => 0)));
end Range_Of_Universal_Integer;

雅各布已经给出了一个完整的答案,但他想添加一个可选的子类型声明:

type A is array (1 .. 10) of Integer;

subtype A_Lengths is Integer range 0 .. A'Length;
subtype A_Range   is Integer range A'Range;

function Image is
     new List_Image (Length_T  => A_Lengths,
                     Index_T   => A_Range,
                     Element_T => Integer,
                     Array_T   => A);

通过为数组索引创建命名子类型来简化问题。

subtype Index_Type is Integer range 1..10;
type A is array(Index_Type) of Integer;

function Array_Image is new List_Image 
  ( Length_T  => Natural,
    Index_T   => Index_Type,
    Element_T => Integer,
    Array_T   => A);