First Steps


Lisp syntax is very simple: there are few rules to remember.

Syntax is made up of S-expressions. An S-expression is either an atom or a list.

Atoms can be numbers like 10, 3.14, or symbols like t (the truth constant), +, my-variable. There’s also a special kind of symbol called keywords, which are colon-prefixed symbols like :thing or :keyword. Keywords evaluate to themselves: you can think of them sort of like enums.

Hello, World!

Without further ado:

CL-USER> (format t "Hello, world!")
Hello, world!


;; Single line comments start with a semicolon, and can start at any point in the line

  This is a multi-line comment.

    They can be nested!