Re: Region argument

[Juri Linkov <juri@linkov.net>]

>> We could start by having Someone™ "in the know" (hint, hint) describe
>> the new conventions in the ELisp manual.
>
> I remember we discussed a new convention, but I'm not sure if we did end
> up implementing one.

IIRC, the missing piece is just a small function:

  (defun region ()
    (funcall region-extract-function 'bounds))

to provide all info including former region-beginning and region-end
for ordinary regions as well as a list of boundaries in case of
rectangular regions.  Then it could be used in the interactive spec:

  (defun occur (regexp &optional nlines region)
    (interactive
     (nconc (occur-read-primary-args)
            (list (and (use-region-p) (region)))))
    (occur-1 regexp nlines (list (current-buffer))))

Here nconc for occur-read-primary-args complicates the issue a little,
but in the general case what is needed is only

  (interactive (list (and (use-region-p) (region))))