c++枚举变量初始值

#include <iostream>     // std::cout, std::boolalpha, std::noboolalpha

enum foo {
    c = -1,
    a = 1,
    b = 2,
};

int main () {
    foo bar;
    std::cout << "initial value is " << bar << std::endl;
    std::cout << std::boolalpha << (bar<a) << std::endl;
    std::cout << std::boolalpha << (bar<c) << std::endl;
}

输出结果：

initial value is 0
true
false