C语言中文网:http://c.biancheng.net/view/595.html
C++官网(英文版):http://www.cplusplus.com/reference/iterator/ostream_iterator/
C++英文网:https://en.cppreference.com/w/cpp/iterator/istream_iterator
C++中文网:https://zh.cppreference.com/w/%E9%A6%96%E9%A1%B5 (https://zh.cppreference.com/w/首页)
关键字:typedef: https://www.cnblogs.com/phpandmysql/p/10816949.html
关键字:typename: https://blog.csdn.net/vanturman/article/details/80269081