Robuta

https://llvm.org/doxygen/classllvm_1_1formatted__raw__ostream.html

https://www.boost.org/doc/libs/1_80_0/doc/html/boost/date_time/ostream_month_formatter.html

https://www.hackerrank.com/challenges/overloading-ostream-operator/leaderboard?page=2512

https://www.hackerrank.com/challenges/overloading-ostream-operator/leaderboard?page=2548