Re: Add/remove an element into/from a cons.

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 12:58 PM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> > How can I add/remove an element into/from a cons, taking the following
> > one as an example:
> >
> > ```emacs-lisp
> > (setq company-backends '((company-tabnine :separate company-capf
> > company-dabbrev company-keywords company-files company-ispell)))
> > ```
> >
> > How can I  remove `company-ispell` from and re-add it into the
> > company-backends defined above?
>
> You can use `setf' with the place being the alist entry like this
> (company-backends replaced with th/test in my example):
>
> --8<---------------cut here---------------start------------->8---
> (setq th/test '(( company-tabnine :separate company-capf company-dabbrev
>                   company-keywords company-files company-ispell)))
>
> (let ((place (assoc 'company-tabnine th/test)))
>   (setf place (remove 'company-ispell place)))
> --8<---------------cut here---------------end--------------->8---

Yes. It does the trick:

`C-j' (setq th/test '((company-tabnine :separate company-capf company-dabbrev
                 company-keywords company-ispell company-files)))

;; ((company-tabnine :separate company-capf company-dabbrev
company-keywords company-ispell company-files))


`C-j' (setq th/test (let ((place (assoc 'company-tabnine th/test)))
        (setf place (remove 'company-ispell place))))

;; (company-tabnine :separate company-capf company-dabbrev
company-keywords company-files)

But how to add it back to the alist?

HZ