Subject: Using occur to list occurrencies of the symbol at point

From: [email-masked] (Niels Möller)
Date: Thu, 01 Mar 2012 11:10:06 +0100

Hi,

I'm using both M-x grep and M-x occur quite a lot. I have been a bit
annoyed that they interpret a prefix argument very differently. With C-u
M-x grep, it searches for the symbol (or word or tag; I'm not sure
exactly how it's delimited) under point, which is a feature I find very
useful.

I first expected C-u M-x occur to behave the same way, but instead it
interprets the prefix argument as the amount of additional context to
include in the output buffer. This is a feature I don't need very often.
I'm not sure it's a good idea to change the behaviour of M-x occur, so
instead I wrote the following function to do what I want:

(defun occur-tag (regexp nlines)
  (interactive
   (let ((tag (funcall (or find-tag-default-function
			   (get major-mode 'find-tag-default-function)
			   'find-tag-default))))
     (if tag
	 (list (concat "\\_<" (regexp-quote tag) "\\_>")
	       (when current-prefix-arg
		 (prefix-numeric-value current-prefix-arg)))
       (occur-read-primary-args))))
  (occur regexp nlines))

It gets the symbol under point in the same way as M-x grep, and
constructs a regexp to use with occur. I this it mainly for searching in
source files, which is why I use \_< and \_> rather than \< and \> when
constructing the regexp.

Maybe it would make sense to add something like this to emacs, either as
a separate function like above, or in response to an "empty" prefix
argument to M-x occur.

Or maybe there's already some emacs function which does this and does it
better, which I'm not aware of...

BTW, I think it would also make some sense with a helper function for
the logic involving find-tag-default-function, since this seems to be
duplicated in find-tag-tag, complete-tag, grep-tag-default, and possibly
other places. Or movee it inside find-tag-default, if those variables
always should be consulted.

Best regards,
/Niels Möller

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