Improve and normalize variable names

[Chadtech]

There are a lot of functions that have parameters named things like "idx" and "l". I think "index" and "list" are better names. It's not like white space is scarce in this project. At the very least, there should be one strategy to variable naming in this repo.

What do you think? Is there value in making this change to the repo? What should the variable names be?