What's the difference between lisp and other languages that you like a lot?

“Programming in Lisp is like playing with the primordial forces of the universe. It feels like lightning between your fingertips. No other language even feels close.” — Glenn Ehrlich, Road to Lisp

The Lisp family of languages is really in a class of its own. I could rant forever about why I am in love with it, but I’ll try to keep this short and in laymen’s terms. 

Lisp is beautiful to me because there is very little built in to the core language, and yet the language itself is designed to be extremely extensible. In other words, it’s extremely simple, and yet you have the ability to grow the language into whatever you want. And it feels so liberating and empowering to be able to do so much with so little. 

In fact, Lisp is extensible because it is so simple. One of Lisp’s great epiphanies is “code as data”. Here is a Lisp program that adds the numbers 2 and 3: 

(+ 2 3) 

When interpreted as code, this says “add 2 and 3” and results in 5. But you can also interpret this as data, in which case it is “the list containing +, 2, and 3”. 

The great epiphany this leads to is that you can easily write code that writes code. This allows you to extend the Lisp language in ways that you couldn’t extend other languages. Because you can write code that writes code (that writes code that writes code…), you can grow the language, extend it, and make it into the language you need. It’s said that by the time you finish a project in Lisp, Lisp has become the language best suited to that project. 

Well, this ended up a little longer than I wanted to. A lot of this is somewhat oversimplified, but I hope I got my point across, and you got a glimpse of why I have such a love affair with Lisp.