const & constexpr

https://www.sourcetrail.com/blog/const_friend_or_foe_in_cpp/

https://www.studytonight.com/cpp/const-keyword.php

https://www.cprogramming.com/tutorial/const_correctness.html

https://docs.microsoft.com/en-us/cpp/cpp/const-cpp?view=vs-2019

https://dydtjr1128.github.io/cpp/2020/01/08/Cpp-const.html

https://www.cppkorea.org/CppCoreGuidelines/Const/

https://m.blog.naver.com/PostView.nhn?blogId=taeil34&logNo=220750240362&proxyReferer=https:%2F%2Fwww.google.com%2F

https://blankspace-dev.tistory.com/344

http://egloos.zum.com/sweeper/v/3147813

https://mommoo.tistory.com/14

https://langgeek.tistory.com/entry/Effective-C-%ED%95%AD%EB%AA%A9-3-%EB%82%8C%EC%83%88%EB%A7%8C-%EB%B3%B4%EC%9D%B4%EB%A9%B4-const%EB%A5%BC-%EB%93%A4%EC%9D%B4%EB%8C%80-%EB%B3%B4%EC%9E%90

https://stackoverflow.com/questions/13103755/intellisense-the-object-has-type-qualifiers-that-are-not-compatible-with-the-me