Re: Advantage using mapc over dolist

[Tomas Hlavaty <tom@logand.com>]

On Mon 02 Dec 2024 at 22:07, Tomas Hlavaty <tom@logand.com> wrote:
> (defun tempo-is-user-element (element)
>   "Try all the user-defined element handlers in `tempo-user-elements'."
>   ;; Sigh... I need (some list)
>   (catch 'found
>     (mapc (lambda (handler)
>             (let ((result (funcall handler element)))
>               (if result (throw 'found result))))
> 	  tempo-user-elements)
>     (throw 'found nil)))
>
> although in Common Lisp, I would avoid catch, throw and mapc and used
> dolist with return or return-from instead:
>
> (defun tempo-is-user-element (element)
>   (dolist (handler tempo-user-elements)
>     (let ((z (funcall handler element)))
>       (when z
>         (cl-return z)))))
>
> This is more readable than the catch, mapc, throw code in Emacs.
>
> Unfortunately, cl-return-from does not seems to be as convenient.
> cl-return might do what I expect cl:return to be doing.

and as the comment in tempo-is-user-element says, this is also nice
example, how longing for "liberating feeling" leads to duplicating the
same code all over the place, badly.  If only there was SOME in Emacs
lisp instead of cl-lib?  Such a simple and useful function.  It even
does not have keyword arguments.