Ada中子类型的非连续范围？ [英] Non-contiguous ranges for subtypes in Ada?

问题描述

作为一种Ada类型系统的学习练习，我试图制作3种类型（或更确切地说，是一种类型和2种亚型）：

Totally as an Ada-type-system learning exercise, I was trying to make 3 types (or rather, a type and 2 subtypes):

• Month_Type ，所有月份的枚举


• Short_Month_Type ， Month_Type 子类型只有30天的月份


• February_Month_Type ，只是2月的子类型

• Month_Type, an enumeration of all months
• Short_Month_Type, a Month_Type subtype only having the months with 30 days
• February_Month_Type, a subtype with just February

似乎子类型必须使用 range 机制，正确？ （还有其他类型的子类型吗？）为了使其能够使用连续范围，我必须按以下顺序放置 Month_Type 枚举：

It seems that subtypes must use the range mechanism, correct? (Is there any other kind of subtype?) In order to get it to work with contiguous ranges, I had to put my Month_Type enumeration in this order:

   type Month_Type is (February, April, June, September, November, January, March, May, July, August, October, December);

显然，这不是几个月的自然顺序，我可以看到人们/我都在努力 Month_Type'First 或期望获得一月份的东西。

Obviously this isn't the natural order of months, and I could see people/me trying to do Month_Type'First or something expecting to get January.

因此，这个愚蠢的例子有两个普遍的问题：

So, two general questions from this silly example:

1. 我可以有一个指定基本类型而不是范围的特定子类型的子类型吗？


2. 可以我以某种方式隐藏了放置月份的顺序的实现细节（例如，使第一个不可见）？

谢谢！

推荐答案

否，枚举 子类型仅允许 range_constra int ，但您可以创建任意数量的集合使用 Ada.Containers.Ordered_Sets 。在此处和此处。

No, an enumeration subtype only admits a range_constraint in this context, but you could create any number of Sets using Ada.Containers.Ordered_Sets. There are examples here and here.

这篇关于Ada中子类型的非连续范围？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！