#include 
    
          // std::cout, std::boolalpha, std::noboolalphaenum foo {    c = -1,    a = 1,    b = 2,};int main () {    foo bar;    std::cout << "initial value is " << bar << std::endl;    std::cout << std::boolalpha << (bar
     
      << std::endl;    std::cout << std::boolalpha << (bar
      
       << std::endl;}
      
     
    

输出结果：

initial value is 0truefalse