It's funny seeing this at the top of HN today. I just wrote a utility in Rust this past weekend to calculate the Shannon and metric entropy of a file (https://github.com/tuxxy/entropy/).
I really love the Shannon entropy equation. I don't know why, but I just find it so fascinating and elegant. I love it so much that I even got it tattooed on my wrist recently haha! (https://twitter.com/__tux/status/1257737842308022275/photo/1)