Re: Using variable names in a macro

[Narendra Joshi]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Narendra Joshi <narendraj9@gmail.com> writes:
>
>> ```
>> (defmacro do-when-idle (f g interval)
>>   "Call F when idle for INTERVAL seconds and then G when there is activity."
>>   `(progn
>>      (defun ,(intern (concat "do-when-idle-"
>>                              (sha1 (format "%s-%s" f g)))) ()
>>        (funcall ,g)
>>        (remove-hook 'post-command-hook
>>                     #',(intern (concat "do-when-idle-"
>>                                        (sha1 (format "%s-%s" f g)))))
>>        (run-with-idle-timer ,interval
>>                             nil
>>                             (lambda ()
>>                               (funcall ,f)
>>                               (add-hook 'post-command-hook
>>                                         #',(intern (concat "do-when-idle-"
>>                                                            (sha1 (format 
>> "%s-%s" f g))))))))
>>      (run-with-idle-timer ,interval
>>                           nil
>>                           (lambda ()
>>                             (funcall ,f)
>>                             (add-hook 'post-command-hook
>>                                       #',(intern (concat "do-when-idle-"
>>                                                          (sha1 (format 
>> "%s-%s" f g)))))))))
>> ```
>
> Hmm, with some trivial simplifications of the list building, this could
> look like:
>
> #+begin_src emacs-lisp
> (defmacro do-when-idle (f g interval)
>   "Call F when idle for INTERVAL seconds and then G when there is activity."
>   (let* ((name (intern (concat "do-when-idle-"
>                                (sha1 (format "%s-%s" f g)))))
>          (run-idle-timer-form `(run-with-idle-timer
>                                 ,interval
>                                 nil
>                                 (lambda ()
>                                   (funcall ,f)
>                                   (add-hook 'post-command-hook #',name)))))
>     `(progn
>        (defun ,name ()
>          (funcall ,g)
>          (remove-hook 'post-command-hook #',name)
>          ,run-idle-timer-form)
>        ,run-idle-timer-form)))
> #+end_src
This is a lot cleaner. Thanks! :)

> It would be better, though, to replace the run-idle-timer-form from with
> a lambda, to avoid the code duplication.
>
> Actually, `do-when-idle' doesn't even have to be a macro.  You can make
> it a defun when you define the NAME with defalias.  Bind it to a closure
> so that you can refer to all of the stuff with variables bound around
> it.
Can you share an example please? :)

-- 
Narendra Joshi