I agree, I read the first sample almost instantly, and I'm only _pretty sure_ I follow the second one after staring at it for a minute. Changing it to a range+f

I agree, I read the first sample almost instantly, and I'm only _pretty sure_ I follow the second one after staring at it for a minute. Changing it to a range+filter+fold would make it an order of magnitude easier to read for me. I do agree with the rest of the article. It's the same stuff I've been doing since reading Clean Code over a decade ago. This gets me thinking, there really is an opportunity cost associated with spending a lot of time working with sequence abstractions and immutable data structures. The better I get at reading immutable code, the harder it is to read code with mutation.