clojure.core/comment

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Type: macro Added: Clojure 1.0 Examples: 4 Runnable: 1

([& body])

Ignores body, yields nil

Examples

by gstamp on 2010-07-17 ▶

;; The commented forms do not get executed (comment (functioncall-1) (functioncall-2)) nil

by jafingerhut on 2014-11-19 . May have evaluation errors. ▶

;; What is inside the (comment ...) form is not completely ignored. Clojure ;; still tries to use the normal reader to read it, so it must consist of ;; a sequence of readable forms with balanced parens, braces, square brackets, ;; with no unreadable elements. ;; If you want lines to be completely ignored, you must use a ; to comment from ;; the ; until the end of the line. If you want to quickly comment or uncomment ;; a range of consecutive lines, most text editors have special commands ;; specifically for that. e.g. Emacs has comment-region ;; http://www.gnu.org/software/emacs/manual/html_node/emacs/Comment-Commands.html ;; Vim has visual commands to do this, and probably many other text editors. ;; (Feel free to edit this text to add links to docs for other editors). ;; What is inside the (comment ...) is readable, so no error for this, ;; and no code will be generated by the compiler. (comment (defn foo [x] (inc x)) ) ;; What is inside the (comment ...) is NOT readable, so this will give an error (comment a : b )

by fordsfords on 2014-11-23 . May have evaluation errors. ▶

;; Another thing to watch out for: the comment form IS a form, and is usually ;; the wrong way to comment out code. For example, let's say that you want to ;; try out a new "then" form in an "if": (if true (comment :old-then) :new-then) ;;=> nil (Oops, :new-then was desired.) ;; Instead, use the "ignore next form" reader macro #_: (if true #_(:old-then) :new-then) ;;=> :new-then ;; Note that #_ also allows non-readable code: #_(a : b) 1 ;;=> 1 (contrast to (comment a : b) which doesn't compile.)

by loeschzwerg on 2019-07-12 . May have evaluation errors. ▶

;; You can use comment to work with a journal ;; (but beware if you want to denote it as a journal) (comment) ;; works (comment ^:journal []) ;; works ;; Doesn't work (comment ^:journal ;; I did some really cool stuff ) ERROR Could not Read: Unmatched delimiter ).

Note by Pete

it doesn't 100% ignore the body. If your comment has a map in it, for example, and that map isn't 100% correct it will fail to compile in some environments. I found that using Light Table. I am certain it would fail on other platforms that won't know to exclude it before parsing.

Example: (comment here is some TeX: \frac{\sum_{m=1}^{m}x_{m}}{x_{s}} )

That will produce an error.

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