Seibel: Many people will agree with you that, yes, it’s more fun to write the code yourself. But other than the fun—
Knuth: It’s not only fun. The job of a mathematician is to make proofs but almost never, when you’re solving a mathematical problem, do you find a theorem for which the hypotheses are exactly what you need for the problem you’re solving. Almost always you’ve got something that’s sort of like the theorem that’s in the book. So what you do is you look at the proof of that theorem and you say, “Oh, here’s how I have to change that proof in order to prove the hypothesis that I really have.” So mathematical books are packed with theorems, but you never plug in exactly the theorem—you want to see that proof because it’s one time in a hundred when you’ll find just the theorem that you wanted. I think it’s exactly the same with software.
选自：Peter Seibel. Coders at Work : Reflections on the Craft of Programming. APress, 2009。中译本将由人民邮电出版社图灵公司翻译出版。