Martin Fowler

Duplication means that every time you read these copies, you need to read them carefully to see if there’s any difference

One way of dealing with future changes is to put flexibility mechanisms into the software

Repeatedly, I saw people only understand what they really needed from software once they’d had a chance to use it, and saw the impact it made to their work.

, I can see a dozen parameters I could add to that function

h. Adding all those parameters complicates the function for the one case it’s used right now

The first foundation for refactoring is self-testing code

A common concern with refactoring is the effect it has on the performance of a program.

. The secret to fast software, in all but hard real-time contexts, is to write tunable software first and then tune it for sufficient speed.

I’ve seen three general approaches to writing fast software

Then we measured performance using Kent’s profiler. None of the possibilities I had thought of had anything to do with the problem. Instead, we found that the system was spending half its time creating instances of date. Even more interesting was that all the instances had the same couple of values.