Clojure: Comment Syntax

By Xah Lee. Date: . Last updated: .

Line Comment

Comment start with SEMICOLON to end of line.

; comment start with semicolon
;; by lisp convention
;; comment on a line by itself start with 2 semicolons

(+ 3 4) ; comment after a expression start with one semicolon

Block Comment

Comment can also be written as (comment …), but the comment body must be a valid lisp syntax, cannot be any character. This returns nil.

;; comment can also be written as (comment …)
(comment this is a
block comment.
  (comment block comment can be nested.)
)
;; comment body must be valid clojure syntax.
;; a semicolon by itself is not
(comment : )
;; compiler error

You usually use this form (comment …) to comment out a block of Clojure code.

;; (comment …) is usually used to comment out block of code
(comment
  (+ 3 4)
)