Why I Program in Lisp

Summary

Lisp is not the most popular language. It never was. Other general purpose languages are more popular and ultimately can do everything that Lisp can (if Church and Turing are correct). They have more libraries and a larger user community than Lisp does. They are more likely to be installed on a machine than Lisp is. Yet I prefer to program in Lisp. I keep a Lisp REPL open at all times, and I write prototypes and exploratory code in Lisp. Why do I do this? Lisp is easier to remember, has fewer limitations and hoops you have to jump through, has lower “friction” between my thoughts and my program, is easily customizable, and, frankly, more fun. Lisp's dreaded Cambridge Polish notation is uniform and universal. I don't have to remember whether a form takes curly braces or square brackets or what the operator precedency is or some weird punctuated syntax that was invented for no good reason. It is (operator operands ...) for everything. Nothing to remember. I basically stopped noticing the parenthesis 40 years ago. I can indent how I please. I program mostly functionally, and Lisp has three features that help out tremendously here. First, if you avoid side effects, it directly supports the substitution model. You can tell Lisp that when it sees this simple form, it can just replace it with that more complex one. Lisp isn't constantly pushing you into thinking imperatively. Second, since the syntax is uniform and doesn't depend on the context, you can refactor and move code around at will. Just move things in balanced parenthesis and you'll pretty much be ok. Third, in most computer languages, you can abstract a specific value by replacing it with a variable that names a value. But you can perform a further abstraction by replacing a variable that names a quantity with a function that computes a quantity. In functional programming, you often downplay the distinction between a value and a function that produces that value. After all, the difference is only one of time spe...