c - C 程序中枚举的使用

Question

对于代码:

void main()
{
   enum a{a,b ,MAX};
   printf("%d",MAX);
}

为什么输出是2在这种情况下？

Answer 1

输出为 2，因为 MAX 为 2。枚举用于为常量创建名称。在 C 中，如果没有显式指定枚举中的某个项目的值，则如果它是第一项，则该值为 0；对于后续项目，该值为 0。因此，在本例中:a 为 0，b 为 1，MAX 为 2。

仅供引用:枚举就像一堆#define，只不过值不需要是常量。请参阅the entry on enumerations in the GNU C manual ，假设您使用 GNU C。

就分配给标识符的值而言，C99 标准有这样的规定(6.7.2.2/3 节):

The identifiers in an enumerator list are declared as constants that have type int and may appear wherever such are permitted. An enumerator with = defines its enumeration constant as the value of the constant expression. If the first enumerator has no =, the value of its enumeration constant is 0. Each subsequent enumerator with no = defines its enumeration constant as the value of the constant expression obtained by adding 1 to the value of the previous enumeration constant. The use of enumerators with = may produce enumeration constants with values that duplicate other values in the same enumeration.