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为什么没有非整数枚举？

发布于 2024-07-15 01:23:04 字数 170 浏览 5 评论 0原文

为什么不能创建非整数枚举？我想知道这是否是语言设计决策，或者在编译器中实现此决策是否存在问题。

换句话说，在语言中实现非整数枚举是否可行，但只是没有合理的需求？或者，如果它不可行但合理，那么有什么障碍？

请有人告诉我 C# 中没有此功能的原因或基本原理，非常感谢。

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木落 2024-07-22 01:23:04

没有技术原因无法做到这一点，但是，我们实际上更多地讨论一组常量（也许在公共名称空间内，如果它们相关的话）。

在枚举中，数值通常是次要的。

下面：

enum Fruit {
  Apple,
  Orange,
  Pear,
  Peach
}

我们仅描述一组命名常量。我们说的是 Fruit 类型的变量可以采用这四个值之一。每个整数值是多少，实际上并不相关。只要我只用名称来引用它们，代表 Apple 的值是 0、1、32、-53 还是 0.002534f 都没关系。

大多数语言确实允许您指定代表每个语言的值，但这实际上是次要的。它有时很有用，但它不是枚举核心目的的一部分。它们只是为您提供一组相关的命名常量，而无需为每个常量指定整数 ID。

此外，枚举通常用于指定可以与按位运算组合的可选标志。如果每个值都由整数表示（那么您只需选择一个使用所需位模式的整数），那么实现起来很简单。
浮点值在这种情况下没有用处。（按位和/或运算对浮点值没有多大意义）

There's no technical reason why it couldn't be done, but then, we are really more talking about a set of constants (perhaps within a common namespace, if they're related).

In an enum, the numerical value is generally secondary.

In the following:

enum Fruit {
  Apple,
  Orange,
  Pear,
  Peach
}

we are only describing a set of named constants. We are saying that a variable of type Fruit can take one of these four values. What the integer value of each one is, is really not relevant. As long as I only refer to them by name, it doesn't matter if the value representing Apple is 0, 1, 32, -53 or 0.002534f.

Most languages do allow you to specify the value that should represent each, but that's really secondary. It's sometimes useful, but it's not part of the core purpose with enums. They are simply there to give you a set of related named constants without having to specify an integer ID for each.

Further, enums are often used to specify optional flags that can be combined with bitwise operations. That is trivial to implement if each value is represented by an integer (then you just have to pick an integer that uses the bit pattern you want).
Floating-point values wouldn't be useful in this context. (bit-wise and/or operations don't make much sense on floating-point values)

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黯然#的苍凉 2024-07-22 01:23:04

我认为枚举是这样创建的，因为与您想要做的相反，枚举并不意味着保存任何有意义的数字表示。

例如，枚举非常适合描述 ff:（

enum Color
{
   Black,
   White,
   Red,
   Yellow,
   Blue,
   //everything else in between
}

诚然，颜色可以用复杂的类型在数字上表示，但暂时请允许我）。心情怎么样？

enum Mood
{
    Happy,
    Giddy,
    Angry,
    Depressed,
    Sad
}

或味道？

enum Taste
{
    Bitter,
    Salty,
    Sweet,
    Spicy
}

我认为你说对了。底线是：枚举旨在表示难以用数字表示的对象或对象特征，或者没有有意义或实用的数字表示——因此可以任意分配给整数，这是最方便的数据类型。

这与假期之类的东西相反，假期在数字上是有意义的。

I think enums were made this way because, as opposed to what you want to do, enumerations weren't meant to hold any meaningful numerical representation.

For example, enums are perfect for describing the ff:

enum Color
{
   Black,
   White,
   Red,
   Yellow,
   Blue,
   //everything else in between
}

(admittedly color can be represented by complex types numerically, but indulge me for the moment). How about mood?

enum Mood
{
    Happy,
    Giddy,
    Angry,
    Depressed,
    Sad
}

or taste?

enum Taste
{
    Bitter,
    Salty,
    Sweet,
    Spicy
}

I think you get the point. Bottomline is: enumerations were meant to represent objects or object characteristics that are difficult to represent numerically, or do not have meaningful or practical numerical representations -- and thus the arbitrary assignment to an integer which is the most convenient data type for such.

This is as opposed to things like holidays, which are numerically meaningful.

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