Re: Human-readable file sorting

[Lars Ingebrigtsen]

John Wiegley <address@hidden> writes:

> If directory-files were made extensible, so a sorting method could be
> provided... that sounds like a nice extension to me. So, having a
> customization variable defaulting to `string-lessp', with an option to switch
> to `string-human-lessp'.

It currently calls `string-lessp' unconditionally, as do all the other
functions that operate on files.  This is a very typical example:

(defun image-mode--images-in-directory (file)
  (let* ((dir (file-name-directory buffer-file-name))
         (files (directory-files dir nil
                                 (image-file-name-regexp) t)))
    ;; Add the current file to the list of images if necessary, in
    ;; case it does not match `image-file-name-regexp'.
    (unless (member file files)
      (push file files))
    (sort files 'string-lessp)))

So I think the easiest way to get all this consistent throughout Emacs
isn't to allow `directory-files' to be customisable, but to instead
introduce a new function `file-string-lessp' (or a better name if you
have it), which would basically look like:

(defun file-string-lessp (s1 s2)
  (pcase file-sorting-method
    (,unicode
     (string-lessp s1 s2))
    (,human
     (human-string-lessp s1 s2)))
    ..)

(Hey!  Did I get the pcase syntax right?  Bonus points!)

Then it's "only a matter" of changing these functions to call
`file-string-lessp', and that would include `directory-files'.

(Perhaps it should be in the C layer for speed?  Does it matter when
sorting files names?  That's probably not the bottleneck...)

> Whether the default should human-lessp is another matter, and something I'd
> instinctively want to defer until feedback.

Sure.

> But having the extensibility does sound nice.

If the proposed method sounds fine, I can start implementing...

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no