1. Introduction: Why Lisp?

If you think the greatest pleasure in programming comes from getting a lot done with code that simply and clearly expresses your intention, then programming in Common Lisp is likely to be about the most fun you can have with a computer. You’ll get more done, faster, using it than you would using pretty much any other language.

That’s a bold claim. Can I justify it? Not in a just a few pages in this chapter—you’re going to have to learn some Lisp and see for yourself—thus the rest of this book. For now, let me start with some anecdotal evidence, the story of my own road to Lisp. Then, in the next section, I’ll explain the payoff I think you’ll get from learning Common Lisp.

The CMU folks showed him some demos of stuff they were working on, and he was convinced. He in turn convinced his bosses to let his team take over the failing project and do it in Lisp. A year later, and using only what was left of the original budget, his team delivered a working application with features that the original team had given up any hope of delivering. My dad credits his team’s success to their decision to use Lisp.

Now, that’s just one anecdote. And maybe my dad is wrong about why they succeeded. Or maybe Lisp was better only in comparison to other languages of the day. These days we have lots of fancy new languages, many of which have incorporated features from Lisp. Am I really saying Lisp can offer you the same benefits today as it offered my dad in the 1980s? Read on.

So I knew two languages inside and out and was familiar with another half dozen. Eventually, however, I realized my interest in programming languages was really rooted in the idea planted by my father’s tales of Lisp—that different languages really are different, and that, despite the formal Turing equivalence of all programming languages, you really can get more done more quickly in some languages than others and have more fun doing it. Yet, ironically, I had never spent that much time with Lisp itself. So, I started doing some Lisp hacking in my free time. And whenever I did, it was exhilarating how quickly I was able to go from idea to working code.

For example, one vacation, having a week or so to hack Lisp, I decided to try writing a version of a program—a system for breeding genetic algorithms to play the game of Go—that I had written early in my career as a Java programmer. Even handicapped by my then rudimentary knowledge of Common Lisp and having to look up even basic functions, it still felt more productive than it would have been to rewrite the same program in Java, even with several extra years of Java experience acquired since writing the first version.