如下所示代码:
std::string foo = "foo-string";
std::string bar = "bar-string";
std::vector<std::string> myvector;
myvector.push_back (foo); // copies
myvector.push_back (bar); // moves
std::cout << "myvector contains:";
for (std::string& x:myvector) std::cout << ' ' << x;
std::cout << '\n';
for语句:for (std::string& x:myvector)替换成for (std::string x:myvector)好像对结果没什么影响,这儿的引用符号有什么特殊作用吗?