complexity

When authoring a large system our first concern, always, is to control Complexity.

Aho et al. had it exactly right:

We do battle with the dragon of complexity every day.

If you see a system starting to get away from you, starting to get too complex, don’t let it. Find a way to reorganize or refactor, so the top-level code is short, using nouns & verbs from the problem domain.

Pay attention to coupling. The nice thing about a short function that does one thing well is it won’t need dozens of variables interacting with one another. Upon exiting, its local variables disappear in a puff of smoke.

Eliminate repeated boilerplate . Identify the concept your copy-pasta code is addressing, pick a good name for it, then re-factor it out.

If you let code become too complex or data flow become too obscure, you’ll be faced with a system that no one properly understands. And then all the “-ilities”, like maintainability, go out the window.