有人咨询C++小程序的问题，记录一下

$ cat mydate.cpp
/* C++ Puzzle */
class MyDate
{
public:
        MyDate() {}
        MyDate(MyDate&) {}
};

int main(void)
{
        MyDate x;
        MyDate y = MyDate(x);
        return 0;
}

/*

$ g++ -Wall mydate.cpp
mydate.cpp: In function `int main()':
mydate.cpp:12: error: no matching function for call to
`MyDate::MyDate(MyDate)'
mydate.cpp:6: note: candidates are: MyDate::MyDate(MyDate&)

*/

Q: How to fix it?
A: Blah, blah, ...