GNU bug report logs - #49316
Add apply-partially's right version

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Message #40 received at 49316 <at> debbugs.gnu.org (full text, mbox):

From: daanturo <daanturo <at> gmail.com>
To: Michael Heerdegen <michael_heerdegen <at> web.de>
Cc: 49316 <at> debbugs.gnu.org
Subject: Re: bug#49316: Add apply-partially's right version
Date: Sat, 3 Jul 2021 13:17:50 +0700

That's cool! Can you submit the patch?

On 7/3/21 10:06 AM, Michael Heerdegen wrote:
> A placeholder (e.g. the symbol `_' which should normally be unbound)
> stands for an argument that is used from the args provided in the actual
> call:
>
> #+begin_src emacs-lisp
> (defmacro applying-partially (call)
>    (let ((args (make-symbol "args")))
>      `(lambda (&rest ,args)
>         (apply #',(car call)
>                ,@(mapcar (lambda (arg)
>                            (if (eq arg '_)
>                                `(pop ,args)
>                              arg))
>                          (cdr call))
>                ,args))))
>
> (defalias 'minus-10 (applying-partially (- _ 10)))
>
> (minus-10 120) ;;  ==> 110
>
> (defalias 'my-list-with-some-elts
>    (applying-partially (list 0 _ 2 _ 4)))
>
> (my-list-with-some-elts 'a 'b 'c 'd) ; => (0 a 2 b 4 c d)
>
> (symbol-function 'my-list-with-some-elts)
> ;; => (closure (t) (&rest args)
> ;;      (apply #'list 0 (pop args) 2 (pop args) 4 args))
> #+end_src
>
> -- 
> Daanturo.

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