2020
https://devblogs.microsoft.com/oldnewthing/20200513-00/?p=103745
    https://www.reddit.com/r/cpp/comments/gj3fok/inside_stdfunction_part_1_the_basic_idea/
2019
https://quuxplusone.github.io/blog/2019/05/10/function-ref-vs-string-view/
    https://www.reddit.com/r/cpp/comments/bn4qfe/on_function_ref_and_string_view/