This write up is really good! Are there similar write-ups for things other than text editors? I wonder if only wanted a printable character ASCII editor would

This write up is really good! Are there similar write-ups for things other than text editors? I wonder if only wanted a printable character ASCII editor would simplify things a lot or only a little. And I guess no tabs. > Part 2 Line breaking I don't really understand the problem here. Can't we count the line breaks like anything else? Is it because that's not the values we want in the end? > Part 4: Again, making this into a monoid is pretty easy. You store two copies of the (t, m) pair - one for the simple case, and one for the case where the beginning of the string is in a comment. You also keep two bits to keep track of whether the string ends or begins a comment. In principle, you have to do the computation twice for both cases, whether the first line is a comment or not, but in practice it doesn’t make the computation any more expensive: you compute (t, m) for the first line and for the rest of the string, and just store both the first value and the monoid sum. What if a node of the rope contains an "end comment" and (later) a "("? What should the two pairs of (t, m) be? Now that substring might be entirely inside, outside or partially outside and inside a comment. Although I do understand the general idea of computing the result for all possible initial/input state to achieve paralellism.