Re: Better way to make sure external command exists in the system?

[Emanuel Berg]

Jean Louis wrote:

> Now it is:
>
> (defvar image-default-resize-size "1536")
> (defvar image-resize-sizes '("1536" "1024" "800" "1200" "640"))

Well, the width of a computer image is not a string but
an integer.

>> The *common-lisp-convention* for global variables is
>> disencourage in Elisp.
>
> Yes, those functions are old. Who knows what I knew
> back then.

Yeah, it is always like that...

>> Also, why the strings?
>
> Maybe it works with numbers, but now I changed it to
> completing-read, maybe that is why I placed it as strings.

Don't do that, data should be in its natural, sound state,
then it is up to functions and/or users who use it to convert
it to fit their purposes. And the better everything is, the
less of that is required.

> (defun image-resize-dired ()
>   "Resizes images."
>   (interactive)
>   (let ((files (dired-get-marked-files))
>       (size (completing-read "Size: " image-resize-sizes nil t 
> image-default-resize-size)))
>     (dolist (file files)
>       (image-resize file size))
>     (revert-buffer)))
>
> That way is better, my choice of 1536 is offered, but if
> I delete it, I can complete it with some of other default
> choices. It is very handy to mark files and resize them how
> one wants.

OK, not sure that's the way it is supposed to work but if you
want to innovate, no problem.

> (defun optimize-image-jpg (file)
>   "Optimizes the JPG image with quality 70%"
>   (if (rcd-which-list '("mogrify"))
>       (let ((extension (file-name-extension file)))
>       (when (equal (downcase extension) "jpg")
>         (let* ((file (shell-double-quote file))
>                (command (format "mogrify -sampling-factor 4:2:0 -strip 
> -interlace JPEG -colorspace RGB -quality 70 \"%s\"" file)))
>           (message command)
>           (shell-command command))))
>     (rcd-warning-message "RCD ERROR: `mogrify' not found in $PATH")))
>
> (defun optimize-jpg-images-dired ()
>   "Optimizes JPG images inside of Dired"
>   (interactive)
>   (let ((files (dired-get-marked-files)))
>     (dolist (file files)
>       (optimize-image-jpg file))
>     (revert-buffer)))

geh.el:281: First sentence should end with punctuation
geh.el:281: Argument ‘file’ should appear (as FILE) in the doc string
geh.el:292: First sentence should end with punctuation

Otherwise looks good, I don't have dired-get-marked-files,
rcd-warning-message, rcd-which-list, or shell-double-quote but
I suppose you do...

>>>               (equal (downcase extension) "png"))
>> 
>> Same thing twice, instead do let*.
>
> There I wanted to test first for extension and then to proceed. 

Yes, but put (downcase extension) in a let* and so you don't
have to do it twice. Now you seem to have removed the PNG so
it isn't an issue anymore.

>> Also, why `read-number' and not in interactive?
>
> I often use `completing-read', maybe that may be implemented in
> `interactive' but I don't find it nice that way.

Yes, compare:

(interactive
  `(,(string-to-number
       (completing-read "Digit: " '("11" "12" "13") nil t "11"))))

>> And, no need for globals if they are only used here.
>> Use let* for that as well.
>
> Which globals?

The two global variables.

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