“So when they ask, “How long is it going to take you to put this change in?” you have three answers. The first is the absolute shortest way, changing the one line of code. The second answer is how long it would be using my simple rule of rewriting the subroutine as if you were not going to make that mistake. Then the third answer is how long if you fix that bug if you were actually writing this subroutine in the better version of the program. So you make your estimate someplace between those last two and then every time you get assigned a task you have a little bit of extra time available to make the program better. I think that that makes an incredible difference. It makes for programs that evolve cleanly.”