C++ 枚举中的最大值和最小值
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Max and min values in a C++ enum
提问by Matt
Is there a way to find the maximum and minimum defined values of an enum in c++?
有没有办法在 c++ 中找到枚举的最大和最小定义值？
回答by Jeff Yates
No, there is no way to find the maximum and minimum defined values of any enum in C++. When this kind of information is needed, it is often good practice to define a Last and First value. For example,
不，没有办法在 C++ 中找到任何枚举的最大值和最小值。当需要此类信息时，定义 Last 和 First 值通常是一种很好的做法。例如，
enum MyPretendEnum
{
Apples,
Oranges,
Pears,
Bananas,
First = Apples,
Last = Bananas
};
There do not need to be named values for every value between Firstand Last.
First和之间的每个值不需要命名值Last。
回答by dalle
No, not in standard C++. You could do it manually:
不，不是在标准 C++ 中。你可以手动完成：
enum Name
{
val0,
val1,
val2,
num_values
};
num_valueswill contain the number of values in the enum.
num_values将包含枚举中的值数。
回答by Justsalt
No. An enum in C or C++ is simply a list of constants. There is no higher structure that would hold such information.
不。 C 或 C++ 中的枚举只是一个常量列表。没有更高的结构可以保存此类信息。
Usually when I need this kind of information I include in the enum a max and min value something like this:
通常当我需要这种信息时，我会在枚举中包含一个最大值和最小值，如下所示：
enum {
eAaa = 1,
eBbb,
eCccc,
eMin = eAaaa,
eMax = eCccc
}
See this web page for some examples of how this can be useful: Stupid Enum Tricks
有关这如何有用的一些示例，请参阅此网页：Stupid Enum Tricks
回答by Tiendil
enum My_enum
{
FIRST_VALUE = 0,
MY_VALUE1,
MY_VALUE2,
...
MY_VALUEN,
LAST_VALUE
};
after definition, My_enum::LAST_VALUE== N+1
定义后，My_enum::LAST_VALUE== N+1
回答by wannes
Not automatically, but you can add artificial enum values to signify min and max values, e.g.
不是自动的，但您可以添加人工枚举值来表示最小值和最大值，例如
typedef enum {start_of_colors=-1, eRed, eWhite, eBlue, eGray,
end_of_colors} eListOfTags;
for (eListOfTags i = start_of_colors+1; i < end_of_colors; i++) {
....
}
回答by Wael
you don't even need them, what I do is just I say for example if you have:
你甚至不需要它们，我所做的只是我说，例如，如果你有：
enum Name{val0,val1,val2};
if you have switch statement and to check if the last value was reached do as the following:
如果您有 switch 语句并检查是否达到了最后一个值，请执行以下操作：
if(selectedOption>=val0 && selectedOption<=val2){
//code
}
