在 Clojure 代码注释中; 和; 的区别是什么？

在 Clojure 发表评论时，;和 ;;有什么不同？我看到我的 文本编辑器颜色他们不同，所以我假设有一些名义上的差异。

我还看到 边缘对待他们的方式不同:

; Stripped entirely
;; Appears in text section of marginalia
(defn foobar []
; Appears in code section of marginalia output
;; Again, appears in code section of marginalia output
6)
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I'm not sure (not used Clojure and never heard of this before), but this thread might help.

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no meaning for the language. ; is a reader macro for comment perhaps other tools parse them but "within clojure" they are the same.

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Emacs ; to be used for end-of-line comments and will indent in surprising ways if that is not your intent. ;; does not so I usually use ;;.

Clojure doesn't care - any line is ignored from the ; to EOL.

I believe there is a tradition in CL of using increasing numbers of ; to indicate more important comments/sections.

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最佳答案

There is no difference as far as the interpreter is concerned. Think of ; ;; ;;; and ;;;; as different heading levels.

Here is my personal use convention:

;;;; Top-of-file level comments, such as a description of the whole file/module/namespace


;;; Documentation for major code sections (i.e. groups of functions) within the file.


;; Documentation for single functions that extends beyond the doc string (e.g. an explanation of the algorithm within the function)


; In-line comments possibly on a single line, and possibly tailing a line of code
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There is no difference from a Clojure-perspective. I find that ;; stands out a little better than ;, but that's only my opinion.

Marginalia on the other hand treats them differently because there are times when a comment should remain in the code section (e.g. license) and those are flagged with ;. This is an arbitrary decision and may change in the future.

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In emacs lisp modes including clojure-mode, ;; is formatted with the convention of being at the beginning of a line, and indented as as any other line, based on the context. ; is expected to be used at the end of a line, so emacs will not do what you want it to if you put a single-semicolon comment at the beginning of a line expecting it to tab to the indentation for the present context.

Example:

(let [foo 1]
;; a comment
foo) ; a comment
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Check out the official description of the meaning of ; vs ;; in elisp: since the Clojure indenter is basically the same, it will treat them similarly. Basically, use ; if you are writing a long sentence/description "in the margins" that will span multiple lines but should be considered a single entity. Their example is:

(setq base-version-list                 ; there was a base
(assoc (substring fn 0 start-vn)  ; version to which
file-version-assoc-list))  ; this looks like
; a subversion

The indenter will make sure those stay lined up next to each other. If, instead, you want to make several unrelated single-line comments next to each other, use ;;.

(let [x 99 ;; as per ticket #425
y "test"] ;; remember to test this
(str x y)) ;; TODO actually write this function

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