Thanks a lot for the improvement, but I am still a bit puzzled when I get the the part where you start talking about `rank` and `select`. By rereading it several times I think I know now what this is all about. But the intro could be much smoother (if you care about that). For example here you instantly start to talk about bit sequences.
> For bit sequences, rank(i) counts the number of 1 bits in the first i places. Because normally I never care about bit sequences, my brain completely skipped the word "bit" and I was puzzled why you were now talking so much about bits. I think a sentence that you use a simplification for the introduction, a sequence with only 0 and 1 values, a bit sequence. Thanks for the link to the theory, I think this will make everything more clear as I read it. And I think it is not all that unfamiliar to me, I just never called it by that name. Now at least I know it's about compression.
