相关疑难解决方法(0)

鉴于下面的代码,一切正常.为什么变量d引用int？到底是怎么回事？

int main()
{
    int a= 10;
    int &&b = a+10; // b is int &&
    auto c =b+10; // c is int
    auto &&d = a; // d is int&
    //int &&di = a; // error, as expected
    return (0);
}