the code you don’t write;

“You don’t write code any faster in NeXTSTEP… however, you write about 20% of the code. The code that’s the fastest to write, the code that’s the easiest to maintain, and the code that never breaks is the code you don’t write.” Steve Jobs, MIT Sloan, spring 1992

Generation is free now. Anyone can have ten thousand lines by lunch. Which makes this the only performance metric that got more expensive: the line you decided not to need. Every line you ship is a promise to maintain it, and the machine writing it will not be there at 2 AM.