First Steps

Syntax

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>(formatt"Hello, world!")Hello,world!NIL

Comments

;; 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! |# |#