为什么在#define 同样有效时使用枚举?

问题描述

所以枚举是这样工作的:

enum {错误的，真的}

相当于

int false = 0整数真 = 1

为什么我不将 enum 替换为 #define?

#define FALSE 0#define TRUE 1

对我来说，它们似乎可以互换.我知道 #define 能够处理参数，因此其操作方式与 enum 完全不同.当我们有 #define 在这种情况下时，enum 的主要用途究竟是什么?

如果我猜的话，由于 #define 是一个预处理器特性，enum 将具有一些运行时优势.我离我有多远?

提前致谢.

解决方案

enum 的优势在您有一长串想要映射为数字的事物并且想要成为能够在该列表的中间插入一些东西.例如，您有:

梨 0苹果 1橙子 2葡萄 3桃子 4杏 5

现在你想把 tangerines 放在 oranges 之后.使用#defines，您必须重新定义grapes、peaches 和apricots 的数量.使用枚举，它会自动发生.是的，这是一个人为的例子，但希望它能给你一个想法.

So an enum works like this:

enum {
  false,
  true
}

which is equivalent to

int false = 0
int true = 1

Why wouldn't I substitute enum with #define?

#define FALSE 0
#define TRUE 1

To me, it seems like they are interchangeable. I'm aware that #define is able to handle arguments, hence operates in an entirely different way than enum. What exactly are the main uses of enum when we have #define in this case?

If I were to guess, as the #define is a preprocessor feature, enum would have some runtime advantages. How far off am I?

Thanks in advance.

解决方案

The advantages of enum show up when you have a long list of things you want to map into numbers, and you want to be able to insert something in the middle of that list. For example, you have:

pears 0
apples 1
oranges 2
grapes 3
peaches 4
apricots 5

Now you want to put tangerines after oranges. With #defines, you'd have to redefine the numbers of grapes, peaches, and apricots. Using enum, it would happen automatically. Yes, this is a contrived example, but hopefully it gives you the idea.

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