> For example, the conventional wisdom that functions should be less than a page of text and that they should do one thing and as abstracted as possible actually makes it quite hard to understand what a program does when you aren't familiar with it.

This hasn't been my experience at all. Functions as small as 100 lines can absolutely destroy my comprehension to the point where I need to refactor it into smaller functions to be able to understand it. I'm dealing with one such function (at 200 lines) right now at work.

Well, let me rephrase. I can see what it's doing easily enough. I just have no idea what it's supposed to be doing, on a chunk by chunk basis, because it's all hand rolled search loops and array manipulation.

I also know the final result is incorrect.

I'm sure I'll slap my forehead and wonder why I couldn't see the problem before after I'm done refactoring it.