IO库 8.2

题目：编写一个测试函数，将cin作为参数传入。

 #include <iostream>
 using std::istream;

 istream& func(istream& is)
 {
     std::string buf;
     while (is >> buf) std::cout << buf << std::endl;
     is.clear();
     return is;
 }

 int main()
 {
     istream& is = func(std::cin);
     std::cout << is.rdstate() << std::endl;
     return ;
 }