C++中explicit的用法

https://blog.csdn.net/qq_35524916/article/details/58178072

https://blog.csdn.net/jinjin1062495199/article/details/59184231

https://www.jb51.net/article/107964.htm

https://blog.csdn.net/acdnjjjdjkdckjj/article/details/5644573

https://blog.csdn.net/kezunhai/article/details/38417087

https://www.cnblogs.com/liushui-sky/p/5752348.html