Add/remove an element into/from a cons.

Add/remove an element into/from a cons.

[Hongyi Zhao]

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?

Regards,
HZ

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

[Tassilo Horn]

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---

HTH,
Tassilo

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

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 1:40 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> 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?

I mean: But how to add it back to its original position in the list?

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 1:42 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Tue, Oct 26, 2021 at 1:40 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> >
> > 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?
>
> I mean: But how to add it back to its original position in the list?

BTW, I want to use the above trick to simplify the following function
but failed:

(setq company-backends '((company-tabnine :separate company-dabbrev
company-keywords company-files company-ispell company-capf)))

(defun my-scratch-init ()
  (with-current-buffer "*scratch*"
    (setq-local company-backends
        '((company-tabnine :separate company-capf company-dabbrev
company-keywords company-files)))
    ))

==>

(defun my-scratch-init ()
  (with-current-buffer "*scratch*"
    (setq-local company-backends (let ((place (assoc 'company-tabnine
company-backends)))
                   (setf place (remove 'company-ispell place))))
    ))

HZ

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

[Tassilo Horn]

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?
>
> I mean: But how to add it back to its original position in the list?

This would add it again as the last element:

--8<---------------cut here---------------start------------->8---
(let ((place (assoc 'company-tabnine th/test)))
  (setf place (append place '(company-ispell))))
--8<---------------cut here---------------end--------------->8---

Bye,
Tassilo

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 2:09 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?
> >
> > I mean: But how to add it back to its original position in the list?
>
> This would add it again as the last element:
>
> --8<---------------cut here---------------start------------->8---
> (let ((place (assoc 'company-tabnine th/test)))
>   (setf place (append place '(company-ispell))))
> --8<---------------cut here---------------end--------------->8---

Thanks. But the push doesn't work:

(let ((place (assoc 'company-tabnine th/test)))
  (setf place (push place '(company-ispell))))

Debugger entered--Lisp error: (wrong-number-of-arguments (lambda
(command &optional arg &rest ignored) "`company-mode' completion
backend using Ispell." (interactive (list 'interactive)) (cond ((eql
command 'interactive) (company-begin-backend 'company-ispell)) ((eql
command 'prefix) (if (company-ispell-available) (progn
(company-grab-word)))) ((eql command 'candidates) (let ((words
(company-ispell--lookup-words arg ...)) (completion-ignore-case t))
(if (string= arg "") words (all-completions arg words)))) ((eql
command 'kind) 'text) ((eql command 'sorted) t) ((eql command
'ignore-case) 'keep-prefix))) 0)
  company-ispell()
  (let* ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v))
  (setq place (let* ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v)))
  (let ((place (assoc 'company-tabnine th/test))) (setq place (let*
((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v))))
  (progn (let ((place (assoc 'company-tabnine th/test))) (setq place
(let* ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v)))))
  elisp--eval-last-sexp(nil)
  eval-last-sexp(nil)
  funcall-interactively(eval-last-sexp nil)
  command-execute(eval-last-sexp)

HZ

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

[Tassilo Horn]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

> (defun my-scratch-init ()
>   (with-current-buffer "*scratch*"
>     (setq-local company-backends (let ((place (assoc 'company-tabnine
> company-backends)))
>                    (setf place (remove 'company-ispell place))))
>     ))

setf returns the new value, so here you are setting company-backends to
the modified alist entry, not the alist itself.  This should work:

--8<---------------cut here---------------start------------->8---
(defun my-scratch-init ()
  (with-current-buffer "*scratch*"
    ;; Ensure it has a local variable.  Not sure if it has by default...
    (make-local-variable 'company-backends)
    (let ((place (assoc 'company-tabnine company-backends)))
      (setf place (remove 'company-ispell place)))))
--8<---------------cut here---------------end--------------->8---

Bye,
Tassilo

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

[Tassilo Horn]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

>> This would add it again as the last element:
>>
>> --8<---------------cut here---------------start------------->8---
>> (let ((place (assoc 'company-tabnine th/test)))
>>   (setf place (append place '(company-ispell))))
>> --8<---------------cut here---------------end--------------->8---
>
> Thanks. But the push doesn't work:
>
> (let ((place (assoc 'company-tabnine th/test)))
>   (setf place (push place '(company-ispell))))

Have a look at the docs.  `push' wants the place as second element, and
then you don't need the `setf' anyway.

--8<---------------cut here---------------start------------->8---
(let ((place (assoc 'company-tabnine th/test)))
  (push 'company-ispell place))
--8<---------------cut here---------------end--------------->8---

But note that `push' will add it to the front of the list.

Hm, I just saw that none of my code actually works, i.e., it does not
alter the value of `th/test'.

--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)))

(let ((place (assoc 'company-tabnine th/test)))
  (setf place (append place '(company-ispell))))

(let ((place (assoc 'company-tabnine th/test)))
  (push 'company-ispell place))
--8<---------------cut here---------------end--------------->8---

Aren't alist entries setf-able places?  It seems so, at least:

(let ((val (assoc 'company-tabnine th/test)))
  (setf (assoc 'company-tabnine th/test)
        (remove 'company-ispell val)))

signals a void-function error.

Ah, now I got it.  You must use `alist-get' instead of `assoc' and not
bind the place to a variable but use it explicitly as the first argument
of `setf' which makes sense given that `setf' is a macro determining the
place from its first argument.  So these do actually work:

--8<---------------cut here---------------start------------->8---
(setf (alist-get 'company-tabnine th/test)
      (remove 'company-ispell (alist-get 'company-tabnine th/test)))

(setf (alist-get 'company-tabnine th/test)
      (append (alist-get 'company-tabnine th/test)
              '(company-ispell)))

(push 'company-ispell (alist-get 'company-tabnine th/test))
--8<---------------cut here---------------end--------------->8---

Bye,
Tassilo

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 2:17 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Tue, Oct 26, 2021 at 2:09 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?
> > >
> > > I mean: But how to add it back to its original position in the list?
> >
> > This would add it again as the last element:
> >
> > --8<---------------cut here---------------start------------->8---
> > (let ((place (assoc 'company-tabnine th/test)))
> >   (setf place (append place '(company-ispell))))
> > --8<---------------cut here---------------end--------------->8---
>
> Thanks. But the push doesn't work:
>
> (let ((place (assoc 'company-tabnine th/test)))
>   (setf place (push place '(company-ispell))))

I also tried out the following method:

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

=>

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



> Debugger entered--Lisp error: (wrong-number-of-arguments (lambda
> (command &optional arg &rest ignored) "`company-mode' completion
> backend using Ispell." (interactive (list 'interactive)) (cond ((eql
> command 'interactive) (company-begin-backend 'company-ispell)) ((eql
> command 'prefix) (if (company-ispell-available) (progn
> (company-grab-word)))) ((eql command 'candidates) (let ((words
> (company-ispell--lookup-words arg ...)) (completion-ignore-case t))
> (if (string= arg "") words (all-completions arg words)))) ((eql
> command 'kind) 'text) ((eql command 'sorted) t) ((eql command
> 'ignore-case) 'keep-prefix))) 0)
>   company-ispell()
>   (let* ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v))
>   (setq place (let* ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v)))
>   (let ((place (assoc 'company-tabnine th/test))) (setq place (let*
> ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v))))
>   (progn (let ((place (assoc 'company-tabnine th/test))) (setq place
> (let* ((v (company-ispell))) (\(setf\ quote\) (cons place 'v) v)))))
>   elisp--eval-last-sexp(nil)
>   eval-last-sexp(nil)
>   funcall-interactively(eval-last-sexp nil)
>   command-execute(eval-last-sexp)
>
> HZ



-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 2:21 PM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> > (defun my-scratch-init ()
> >   (with-current-buffer "*scratch*"
> >     (setq-local company-backends (let ((place (assoc 'company-tabnine
> > company-backends)))
> >                    (setf place (remove 'company-ispell place))))
> >     ))
>
> setf returns the new value, so here you are setting company-backends to
> the modified alist entry, not the alist itself.  This should work:
>
> --8<---------------cut here---------------start------------->8---
> (defun my-scratch-init ()
>   (with-current-buffer "*scratch*"
>     ;; Ensure it has a local variable.  Not sure if it has by default...
>     (make-local-variable 'company-backends)
>     (let ((place (assoc 'company-tabnine company-backends)))
>       (setf place (remove 'company-ispell place)))))
> --8<---------------cut here---------------end--------------->8---

It doesn't work. The variable hasn't been revised when I'm switch to
scratch buffer.

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 2:21 PM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> > (defun my-scratch-init ()
> >   (with-current-buffer "*scratch*"
> >     (setq-local company-backends (let ((place (assoc 'company-tabnine
> > company-backends)))
> >                    (setf place (remove 'company-ispell place))))
> >     ))
>
> setf returns the new value, so here you are setting company-backends to
> the modified alist entry, not the alist itself.  This should work:
>
> --8<---------------cut here---------------start------------->8---
> (defun my-scratch-init ()
>   (with-current-buffer "*scratch*"
>     ;; Ensure it has a local variable.  Not sure if it has by default...

The default value is set this way, as I've posted:

(setq company-backends '((company-tabnine :separate company-dabbrev
company-keywords company-files company-ispell company-capf)))

>     (make-local-variable 'company-backends)
>     (let ((place (assoc 'company-tabnine company-backends)))
>       (setf place (remove 'company-ispell place)))))
> --8<---------------cut here---------------end--------------->8---
>
> Bye,
> Tassilo

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 3:09 PM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> >> This would add it again as the last element:
> >>
> >> --8<---------------cut here---------------start------------->8---
> >> (let ((place (assoc 'company-tabnine th/test)))
> >>   (setf place (append place '(company-ispell))))
> >> --8<---------------cut here---------------end--------------->8---
> >
> > Thanks. But the push doesn't work:
> >
> > (let ((place (assoc 'company-tabnine th/test)))
> >   (setf place (push place '(company-ispell))))
>
> Have a look at the docs.  `push' wants the place as second element, and
> then you don't need the `setf' anyway.
>
> --8<---------------cut here---------------start------------->8---
> (let ((place (assoc 'company-tabnine th/test)))
>   (push 'company-ispell place))
> --8<---------------cut here---------------end--------------->8---
>
> But note that `push' will add it to the front of the list.
>
> Hm, I just saw that none of my code actually works, i.e., it does not
> alter the value of `th/test'.
>
> --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)))
>
> (let ((place (assoc 'company-tabnine th/test)))
>   (setf place (append place '(company-ispell))))
>
> (let ((place (assoc 'company-tabnine th/test)))
>   (push 'company-ispell place))
> --8<---------------cut here---------------end--------------->8---
>
> Aren't alist entries setf-able places?  It seems so, at least:
>
> (let ((val (assoc 'company-tabnine th/test)))
>   (setf (assoc 'company-tabnine th/test)
>         (remove 'company-ispell val)))
>
> signals a void-function error.
>
> Ah, now I got it.  You must use `alist-get' instead of `assoc' and not
> bind the place to a variable but use it explicitly as the first argument
> of `setf' which makes sense given that `setf' is a macro determining the
> place from its first argument.  So these do actually work:
>
> --8<---------------cut here---------------start------------->8---
> (setf (alist-get 'company-tabnine th/test)
>       (remove 'company-ispell (alist-get 'company-tabnine th/test)))
>
> (setf (alist-get 'company-tabnine th/test)
>       (append (alist-get 'company-tabnine th/test)
>               '(company-ispell)))
>
> (push 'company-ispell (alist-get 'company-tabnine th/test))
> --8<---------------cut here---------------end--------------->8---

I tried with the following function:

```emacs-lisp
(use-package company-tabnine
  :init
  (setq company-backends '((company-tabnine :separate company-dabbrev
company-keywords company-files company-ispell company-capf)))

  :hook
  (emacs-lisp-mode . hz/scratch-init)

  :config
  (defun hz/scratch-init ()
    (with-current-buffer "*scratch*"
      (make-local-variable 'company-backends)
       (setf (alist-get 'company-tabnine company-backends)
               (remove 'company-ispell (alist-get 'company-tabnine
company-backends)))
     ))
```
The above method will set the correct company-backends when I'm on
scratch buffer. But I also find that when I switch to other buffers,
says, AUCTeX based LaTeX-mode, the company-backends settings still
remains the same, and can't be restored to the default configuration,
i.e., the following:

(setq company-backends '((company-tabnine :separate company-dabbrev
company-keywords company-files company-ispell company-capf)))

HZ

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

[Tassilo Horn]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

> I tried with the following function:
>
> ```emacs-lisp
>   (defun hz/scratch-init ()
>     (with-current-buffer "*scratch*"
>       (make-local-variable 'company-backends)
>        (setf (alist-get 'company-tabnine company-backends)
>                (remove 'company-ispell (alist-get 'company-tabnine
> company-backends)))
>      ))
> ```
>
> The above method will set the correct company-backends when I'm on
> scratch buffer. But I also find that when I switch to other buffers,
> says, AUCTeX based LaTeX-mode, the company-backends settings still
> remains the same,

You mean, the above function changes the value not only in *scratch* but
all buffers?  That shouldn't happen, I'd say, as the function explicitly
makes `company-backends' buffer-local in *scratch* before modifying it.

In any case, I think it would be more valuable for any of us if you'd
start a discussion with a statement on what you want to achieve instead
of some non-working snippet of code where the intent is to be
interpreted by the reader.

Bye,
Tassilo

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 4:59 PM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> > I tried with the following function:
> >
> > ```emacs-lisp
> >   (defun hz/scratch-init ()
> >     (with-current-buffer "*scratch*"
> >       (make-local-variable 'company-backends)
> >        (setf (alist-get 'company-tabnine company-backends)
> >                (remove 'company-ispell (alist-get 'company-tabnine
> > company-backends)))
> >      ))
> > ```
> >
> > The above method will set the correct company-backends when I'm on
> > scratch buffer. But I also find that when I switch to other buffers,
> > says, AUCTeX based LaTeX-mode, the company-backends settings still
> > remains the same,
>
> You mean, the above function changes the value not only in *scratch* but
> all buffers?

After using the above function, it disables me to check the value of
`company-backends'  when I switch from scratch to other buffers. The
following message will be triggered when I call  `C-h v
company-backends RET':

Type "q" to restore previous buffer, SPC to scroll help.


> That shouldn't happen, I'd say, as the function explicitly
> makes `company-backends' buffer-local in *scratch* before modifying it.
>
> In any case, I think it would be more valuable for any of us if you'd
> start a discussion with a statement on what you want to achieve instead
> of some non-working snippet of code where the intent is to be
> interpreted by the reader.

I'm using company-tabnine package and the following company-backends setting:

(setq company-backends '((company-tabnine :separate company-dabbrev
company-keywords company-files company-ispell company-capf)))

I want to disable the company-ispell backend when I'm in
emacs-lisp-mode. The following function will do the trick:

  (defun hz/scratch-init ()
    (with-current-buffer "*scratch*"
       (setq-local company-backends
                 '((company-tabnine :separate company-capf
company-dabbrev company-keywords company-files)))
  ))

(add-hook 'emacs-lisp-mode-hook #'hz/scratch-init)

But as I've posted here, considering that I've also had a definite
company-backends setting, so I want to remove the company-ispell from
it programmatically.

I hope this time I've clearly stated my intention.

HZ

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 5:26 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> But as I've posted here, considering that I've also had a definite
> company-backends setting, so I want to remove the company-ispell from
> it programmatically.
>
> I hope this time I've clearly stated my intention.

The background of the whole question comes from here [1].

[1] https://github.com/company-mode/company-mode/issues/1130#issuecomment-950331890

HZ

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

[Stefan Monnier]

Tassilo Horn [2021-10-26 10:15:29] wrote:
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>> I tried with the following function:
>>
>> ```emacs-lisp
>>   (defun hz/scratch-init ()
>>     (with-current-buffer "*scratch*"
>>       (make-local-variable 'company-backends)
>>        (setf (alist-get 'company-tabnine company-backends)
>>                (remove 'company-ispell (alist-get 'company-tabnine
>> company-backends)))
>>      ))
>> ```
>>
>> The above method will set the correct company-backends when I'm on
>> scratch buffer. But I also find that when I switch to other buffers,
>> says, AUCTeX based LaTeX-mode, the company-backends settings still
>> remains the same,
>
> You mean, the above function changes the value not only in *scratch* but
> all buffers?  That shouldn't happen, I'd say, as the function explicitly
> makes `company-backends' buffer-local in *scratch* before modifying it.

The `setf` above changes the data structure by side-effect.
It does not change the variable itself.


        Stefan

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

[Hongyi Zhao]

On Tue, Oct 26, 2021 at 8:36 PM Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> Tassilo Horn [2021-10-26 10:15:29] wrote:
> > Hongyi Zhao <hongyi.zhao@gmail.com> writes:
> >> I tried with the following function:
> >>
> >> ```emacs-lisp
> >>   (defun hz/scratch-init ()
> >>     (with-current-buffer "*scratch*"
> >>       (make-local-variable 'company-backends)
> >>        (setf (alist-get 'company-tabnine company-backends)
> >>                (remove 'company-ispell (alist-get 'company-tabnine
> >> company-backends)))
> >>      ))
> >> ```
> >>
> >> The above method will set the correct company-backends when I'm on
> >> scratch buffer. But I also find that when I switch to other buffers,
> >> says, AUCTeX based LaTeX-mode, the company-backends settings still
> >> remains the same,
> >
> > You mean, the above function changes the value not only in *scratch* but
> > all buffers?  That shouldn't happen, I'd say, as the function explicitly
> > makes `company-backends' buffer-local in *scratch* before modifying it.
>
> The `setf` above changes the data structure by side-effect.
> It does not change the variable itself.

How can I solve this problem to achieve the same effect as my original function?

HZ

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

[Tassilo Horn]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

>> You mean, the above function changes the value not only in *scratch*
>> but all buffers?
>
> After using the above function, it disables me to check the value of
> `company-backends' when I switch from scratch to other buffers.

What?

> The following message will be triggered when I call `C-h v
> company-backends RET':
>
> Type "q" to restore previous buffer, SPC to scroll help.

Yes, but how does that message hinder you from checking the value of
`company-backends'?

> I'm using company-tabnine package and the following company-backends
> setting:
>
> (setq company-backends '((company-tabnine :separate company-dabbrev
> company-keywords company-files company-ispell company-capf)))
>
> I want to disable the company-ispell backend when I'm in
> emacs-lisp-mode. The following function will do the trick:
>
>   (defun hz/scratch-init ()
>     (with-current-buffer "*scratch*"
>        (setq-local company-backends
>                  '((company-tabnine :separate company-capf
> company-dabbrev company-keywords company-files)))
>   ))
>
> (add-hook 'emacs-lisp-mode-hook #'hz/scratch-init)

Well, your function will always run when `emacs-lisp-mode' or a mode
derived from it, like `lisp-interaction-mode', the major-mode of
*scratch*, is activated.  But it evaluates that code always in *scratch*
which defeats the purpose of disabling company-ispell in every buffer
having `emacs-lisp-mode' as major-mode.

> But as I've posted here, considering that I've also had a definite
> company-backends setting, so I want to remove the company-ispell from
> it programmatically.
>
> I hope this time I've clearly stated my intention.

I guess so.  In certain modes, you would like to have `company-ispell'
removed from the company-tabnine entry of company-backends.  Right?

In that respect, I think a function like

--8<---------------cut here---------------start------------->8---
(defun hz/company-tabnine-remove-company-ispell ()
  (make-local-variable 'company-backends)
  (setf (alist-get 'company-tabnine company-backends)
        (remove 'company-ispell
                (alist-get 'company-tabnine company-backends))))
--8<---------------cut here---------------end--------------->8---

should do the trick.  However, I can imagine that you might not be able
to use it in major-mode hooks such as `emacs-lisp-mode' due to ordering
issues, i.e., I can easily imagine that `company-mode' (and this
company-tabnine thingy) is initialized *after* the major-mode hook has
run because usually, you activate minor-modes in major-mode hooks.  In
that case you would try to remove before the company-tabnine entry has
been added to company-backends.

That's all just guesswork since I don't use company.

Bye,
Tassilo

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

[Hongyi Zhao]

On Wed, Oct 27, 2021 at 3:19 AM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> >> You mean, the above function changes the value not only in *scratch*
> >> but all buffers?
> >
> > After using the above function, it disables me to check the value of
> > `company-backends' when I switch from scratch to other buffers.
>
> What?
>
> > The following message will be triggered when I call `C-h v
> > company-backends RET':
> >
> > Type "q" to restore previous buffer, SPC to scroll help.
>
> Yes, but how does that message hinder you from checking the value of
> `company-backends'?

I can't reproduce this now.

> > I'm using company-tabnine package and the following company-backends
> > setting:
> >
> > (setq company-backends '((company-tabnine :separate company-dabbrev
> > company-keywords company-files company-ispell company-capf)))
> >
> > I want to disable the company-ispell backend when I'm in
> > emacs-lisp-mode. The following function will do the trick:
> >
> >   (defun hz/scratch-init ()
> >     (with-current-buffer "*scratch*"
> >        (setq-local company-backends
> >                  '((company-tabnine :separate company-capf
> > company-dabbrev company-keywords company-files)))
> >   ))
> >
> > (add-hook 'emacs-lisp-mode-hook #'hz/scratch-init)
>
> Well, your function will always run when `emacs-lisp-mode' or a mode
> derived from it, like `lisp-interaction-mode', the major-mode of
> *scratch*, is activated.  But it evaluates that code always in *scratch*
> which defeats the purpose of disabling company-ispell in every buffer
> having `emacs-lisp-mode' as major-mode.
>
> > But as I've posted here, considering that I've also had a definite
> > company-backends setting, so I want to remove the company-ispell from
> > it programmatically.
> >
> > I hope this time I've clearly stated my intention.
>
> I guess so.  In certain modes, you would like to have `company-ispell'
> removed from the company-tabnine entry of company-backends.  Right?
>
> In that respect, I think a function like
>
> --8<---------------cut here---------------start------------->8---
> (defun hz/company-tabnine-remove-company-ispell ()
>   (make-local-variable 'company-backends)
>   (setf (alist-get 'company-tabnine company-backends)
>         (remove 'company-ispell
>                 (alist-get 'company-tabnine company-backends))))
> --8<---------------cut here---------------end--------------->8---
>
> should do the trick.  However, I can imagine that you might not be able
> to use it in major-mode hooks such as `emacs-lisp-mode' due to ordering
> issues, i.e., I can easily imagine that `company-mode' (and this
> company-tabnine thingy) is initialized *after* the major-mode hook has
> run because usually, you activate minor-modes in major-mode hooks.  In
> that case you would try to remove before the company-tabnine entry has
> been added to company-backends.
>
> That's all just guesswork since I don't use company.

I have changed the original function to the following form:

```emacs-lisp
(defun hz/company-tabnine-remove-company-ispell ()
    (setq-local company-backends
        '((company-tabnine :separate company-capf company-dabbrev
company-keywords company-files))))
```

Based on my tries, your above suggest code will set and append the
following value to the current buffer's company-backends:

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

HZ

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

[Hongyi Zhao]

On Wed, Oct 27, 2021 at 9:39 AM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Wed, Oct 27, 2021 at 3:19 AM Tassilo Horn <tsdh@gnu.org> wrote:
> >
> > Hongyi Zhao <hongyi.zhao@gmail.com> writes:
> >
> > >> You mean, the above function changes the value not only in *scratch*
> > >> but all buffers?
> > >
> > > After using the above function, it disables me to check the value of
> > > `company-backends' when I switch from scratch to other buffers.
> >
> > What?
> >
> > > The following message will be triggered when I call `C-h v
> > > company-backends RET':
> > >
> > > Type "q" to restore previous buffer, SPC to scroll help.
> >
> > Yes, but how does that message hinder you from checking the value of
> > `company-backends'?
>
> I can't reproduce this now.
>
> > > I'm using company-tabnine package and the following company-backends
> > > setting:
> > >
> > > (setq company-backends '((company-tabnine :separate company-dabbrev
> > > company-keywords company-files company-ispell company-capf)))
> > >
> > > I want to disable the company-ispell backend when I'm in
> > > emacs-lisp-mode. The following function will do the trick:
> > >
> > >   (defun hz/scratch-init ()
> > >     (with-current-buffer "*scratch*"
> > >        (setq-local company-backends
> > >                  '((company-tabnine :separate company-capf
> > > company-dabbrev company-keywords company-files)))
> > >   ))
> > >
> > > (add-hook 'emacs-lisp-mode-hook #'hz/scratch-init)
> >
> > Well, your function will always run when `emacs-lisp-mode' or a mode
> > derived from it, like `lisp-interaction-mode', the major-mode of
> > *scratch*, is activated.  But it evaluates that code always in *scratch*
> > which defeats the purpose of disabling company-ispell in every buffer
> > having `emacs-lisp-mode' as major-mode.
> >
> > > But as I've posted here, considering that I've also had a definite
> > > company-backends setting, so I want to remove the company-ispell from
> > > it programmatically.
> > >
> > > I hope this time I've clearly stated my intention.
> >
> > I guess so.  In certain modes, you would like to have `company-ispell'
> > removed from the company-tabnine entry of company-backends.  Right?
> >
> > In that respect, I think a function like
> >
> > --8<---------------cut here---------------start------------->8---
> > (defun hz/company-tabnine-remove-company-ispell ()
> >   (make-local-variable 'company-backends)
> >   (setf (alist-get 'company-tabnine company-backends)
> >         (remove 'company-ispell
> >                 (alist-get 'company-tabnine company-backends))))
> > --8<---------------cut here---------------end--------------->8---
> >
> > should do the trick.  However, I can imagine that you might not be able
> > to use it in major-mode hooks such as `emacs-lisp-mode' due to ordering
> > issues, i.e., I can easily imagine that `company-mode' (and this
> > company-tabnine thingy) is initialized *after* the major-mode hook has
> > run because usually, you activate minor-modes in major-mode hooks.  In
> > that case you would try to remove before the company-tabnine entry has
> > been added to company-backends.
> >
> > That's all just guesswork since I don't use company.
>
> I have changed the original function to the following form:
>
> ```emacs-lisp
> (defun hz/company-tabnine-remove-company-ispell ()
>     (setq-local company-backends
>         '((company-tabnine :separate company-capf company-dabbrev
> company-keywords company-files))))
> ```
>
> Based on my tries, your above suggest code will set and append the
> following value to the current buffer's company-backends:
>
> (company-tabnine :separate company-capf company-dabbrev
> company-keywords company-files)

I also tried the following snippet, but still failed:

(defun hz/company-tabnine-remove-company-ispell ()
    (make-local-variable 'company-backends)
    (cond
     (
      (derived-mode-p 'emacs-lisp-mode)
      (setf (alist-get 'company-tabnine company-backends)
            (remove 'company-ispell (alist-get 'company-tabnine
company-backends))))
     (
      t
      (setf (alist-get 'company-tabnine company-backends)
        (append (alist-get 'company-tabnine company-backends)
            '(company-ispell))))))

(add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)

HZ

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

[Hongyi Zhao]

On Wed, Oct 27, 2021 at 12:54 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Wed, Oct 27, 2021 at 9:39 AM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> >
> > On Wed, Oct 27, 2021 at 3:19 AM Tassilo Horn <tsdh@gnu.org> wrote:
> > >
> > > Hongyi Zhao <hongyi.zhao@gmail.com> writes:
> > >
> > > >> You mean, the above function changes the value not only in *scratch*
> > > >> but all buffers?
> > > >
> > > > After using the above function, it disables me to check the value of
> > > > `company-backends' when I switch from scratch to other buffers.
> > >
> > > What?
> > >
> > > > The following message will be triggered when I call `C-h v
> > > > company-backends RET':
> > > >
> > > > Type "q" to restore previous buffer, SPC to scroll help.
> > >
> > > Yes, but how does that message hinder you from checking the value of
> > > `company-backends'?
> >
> > I can't reproduce this now.
> >
> > > > I'm using company-tabnine package and the following company-backends
> > > > setting:
> > > >
> > > > (setq company-backends '((company-tabnine :separate company-dabbrev
> > > > company-keywords company-files company-ispell company-capf)))
> > > >
> > > > I want to disable the company-ispell backend when I'm in
> > > > emacs-lisp-mode. The following function will do the trick:
> > > >
> > > >   (defun hz/scratch-init ()
> > > >     (with-current-buffer "*scratch*"
> > > >        (setq-local company-backends
> > > >                  '((company-tabnine :separate company-capf
> > > > company-dabbrev company-keywords company-files)))
> > > >   ))
> > > >
> > > > (add-hook 'emacs-lisp-mode-hook #'hz/scratch-init)
> > >
> > > Well, your function will always run when `emacs-lisp-mode' or a mode
> > > derived from it, like `lisp-interaction-mode', the major-mode of
> > > *scratch*, is activated.  But it evaluates that code always in *scratch*
> > > which defeats the purpose of disabling company-ispell in every buffer
> > > having `emacs-lisp-mode' as major-mode.
> > >
> > > > But as I've posted here, considering that I've also had a definite
> > > > company-backends setting, so I want to remove the company-ispell from
> > > > it programmatically.
> > > >
> > > > I hope this time I've clearly stated my intention.
> > >
> > > I guess so.  In certain modes, you would like to have `company-ispell'
> > > removed from the company-tabnine entry of company-backends.  Right?
> > >
> > > In that respect, I think a function like
> > >
> > > --8<---------------cut here---------------start------------->8---
> > > (defun hz/company-tabnine-remove-company-ispell ()
> > >   (make-local-variable 'company-backends)
> > >   (setf (alist-get 'company-tabnine company-backends)
> > >         (remove 'company-ispell
> > >                 (alist-get 'company-tabnine company-backends))))
> > > --8<---------------cut here---------------end--------------->8---
> > >
> > > should do the trick.  However, I can imagine that you might not be able
> > > to use it in major-mode hooks such as `emacs-lisp-mode' due to ordering
> > > issues, i.e., I can easily imagine that `company-mode' (and this
> > > company-tabnine thingy) is initialized *after* the major-mode hook has
> > > run because usually, you activate minor-modes in major-mode hooks.  In
> > > that case you would try to remove before the company-tabnine entry has
> > > been added to company-backends.
> > >
> > > That's all just guesswork since I don't use company.
> >
> > I have changed the original function to the following form:
> >
> > ```emacs-lisp
> > (defun hz/company-tabnine-remove-company-ispell ()
> >     (setq-local company-backends
> >         '((company-tabnine :separate company-capf company-dabbrev
> > company-keywords company-files))))
> > ```
> >
> > Based on my tries, your above suggest code will set and append the
> > following value to the current buffer's company-backends:
> >
> > (company-tabnine :separate company-capf company-dabbrev
> > company-keywords company-files)
>
> I also tried the following snippet, but still failed:
>
> (defun hz/company-tabnine-remove-company-ispell ()
>     (make-local-variable 'company-backends)
>     (cond
>      (
>       (derived-mode-p 'emacs-lisp-mode)
>       (setf (alist-get 'company-tabnine company-backends)
>             (remove 'company-ispell (alist-get 'company-tabnine
> company-backends))))
>      (
>       t
>       (setf (alist-get 'company-tabnine company-backends)
>         (append (alist-get 'company-tabnine company-backends)
>             '(company-ispell))))))
>
> (add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)

The function currently used by me to achieve the goal is as follows:

(defun hz/company-tabnine-remove-company-ispell ()
    (when (derived-mode-p 'emacs-lisp-mode)
      (setq-local company-backends
          '((company-tabnine :separate company-capf company-dabbrev
company-keywords company-files)))))

(add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)

HZ

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

[Tassilo Horn]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

>> > However, I can imagine that you might not be able to use it in
>> > major-mode hooks such as `emacs-lisp-mode' due to ordering issues,
>> > i.e., I can easily imagine that `company-mode' (and this
>> > company-tabnine thingy) is initialized *after* the major-mode hook
>> > has run because usually, you activate minor-modes in major-mode
>> > hooks.  In that case you would try to remove before the
>> > company-tabnine entry has been added to company-backends.
>> >
>> > That's all just guesswork since I don't use company.
>>
>> [...]
>
> I also tried the following snippet, but still failed:
>
> (defun hz/company-tabnine-remove-company-ispell ()
>     (make-local-variable 'company-backends)
>     (cond
>      (
>       (derived-mode-p 'emacs-lisp-mode)
>       (setf (alist-get 'company-tabnine company-backends)
>             (remove 'company-ispell (alist-get 'company-tabnine
> company-backends))))
>      (
>       t
>       (setf (alist-get 'company-tabnine company-backends)
>         (append (alist-get 'company-tabnine company-backends)
>             '(company-ispell))))))
>
> (add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)

The first cond clause looks good but I don't see why you need the
t-clause?  Isn't the thing that company-ispell is part of the default
value of the company-tabnine entry of company-backends?  If that's the
case, you want to make company-backends buffer-local and remove it in
emacs-lisp-mode and derived modes but there is no need to add it again
otherwise because the default value won't be altered.  So that'd be:

--8<---------------cut here---------------start------------->8---
(defun hz/company-tabnine-remove-company-ispell ()
  (when (derived-mode-p 'emacs-lisp-mode)
    (make-local-variable 'company-backends))
    (setf (alist-get 'company-tabnine company-backends)
            (remove 'company-ispell
                    (alist-get 'company-tabnine company-backends))))
--8<---------------cut here---------------end--------------->8---

But most importantly, `emacs-startup-hook' is not the one you want.
That runs once after emacs has loaded the init file.  I'm even not sure
what buffer is current then.  I guess the most logical hook is
`company-mode-hook'.

  (add-hook 'company-mode-hook
            #'hz/company-tabnine-remove-company-ispell)

Or maybe there is also some `company-tabnine-*-hook' that runs after
that package has done its setup in a buffer?

Bye,
Tassilo

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

[Hongyi Zhao]

On Thu, Oct 28, 2021 at 2:52 AM Tassilo Horn <tsdh@gnu.org> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> >> > However, I can imagine that you might not be able to use it in
> >> > major-mode hooks such as `emacs-lisp-mode' due to ordering issues,
> >> > i.e., I can easily imagine that `company-mode' (and this
> >> > company-tabnine thingy) is initialized *after* the major-mode hook
> >> > has run because usually, you activate minor-modes in major-mode
> >> > hooks.  In that case you would try to remove before the
> >> > company-tabnine entry has been added to company-backends.
> >> >
> >> > That's all just guesswork since I don't use company.
> >>
> >> [...]
> >
> > I also tried the following snippet, but still failed:
> >
> > (defun hz/company-tabnine-remove-company-ispell ()
> >     (make-local-variable 'company-backends)
> >     (cond
> >      (
> >       (derived-mode-p 'emacs-lisp-mode)
> >       (setf (alist-get 'company-tabnine company-backends)
> >             (remove 'company-ispell (alist-get 'company-tabnine
> > company-backends))))
> >      (
> >       t
> >       (setf (alist-get 'company-tabnine company-backends)
> >         (append (alist-get 'company-tabnine company-backends)
> >             '(company-ispell))))))
> >
> > (add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)
>
> The first cond clause looks good but I don't see why you need the
> t-clause?  Isn't the thing that company-ispell is part of the default
> value of the company-tabnine entry of company-backends?  If that's the
> case, you want to make company-backends buffer-local and remove it in
> emacs-lisp-mode and derived modes but there is no need to add it again
> otherwise because the default value won't be altered.  So that'd be:
>
> --8<---------------cut here---------------start------------->8---
> (defun hz/company-tabnine-remove-company-ispell ()
>   (when (derived-mode-p 'emacs-lisp-mode)
>     (make-local-variable 'company-backends))
>     (setf (alist-get 'company-tabnine company-backends)
>             (remove 'company-ispell
>                     (alist-get 'company-tabnine company-backends))))
> --8<---------------cut here---------------end--------------->8---

A very strange result based on the above code is that it will remove
company-ispell in all modes, say, LaTeX mode. But the following code
works as expected:

(defun hz/company-tabnine-remove-company-ispell ()
    (when (derived-mode-p 'emacs-lisp-mode)
      (setq-local company-backends
          '((company-tabnine :separate company-capf company-dabbrev
company-keywords company-files))
          )))


> But most importantly, `emacs-startup-hook' is not the one you want.
> That runs once after emacs has loaded the init file.  I'm even not sure
> what buffer is current then.  I guess the most logical hook is
> `company-mode-hook'.
>
>   (add-hook 'company-mode-hook
>             #'hz/company-tabnine-remove-company-ispell)

This works. Thank you for pointing this out.

> Or maybe there is also some `company-tabnine-*-hook' that runs after
> that package has done its setup in a buffer?

Unfortunately, it doesn't supply these type hooks.

HZ

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

[Hongyi Zhao]

On Thu, Oct 28, 2021 at 12:14 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Thu, Oct 28, 2021 at 2:52 AM Tassilo Horn <tsdh@gnu.org> wrote:
> >
> > Hongyi Zhao <hongyi.zhao@gmail.com> writes:
> >
> > >> > However, I can imagine that you might not be able to use it in
> > >> > major-mode hooks such as `emacs-lisp-mode' due to ordering issues,
> > >> > i.e., I can easily imagine that `company-mode' (and this
> > >> > company-tabnine thingy) is initialized *after* the major-mode hook
> > >> > has run because usually, you activate minor-modes in major-mode
> > >> > hooks.  In that case you would try to remove before the
> > >> > company-tabnine entry has been added to company-backends.
> > >> >
> > >> > That's all just guesswork since I don't use company.
> > >>
> > >> [...]
> > >
> > > I also tried the following snippet, but still failed:
> > >
> > > (defun hz/company-tabnine-remove-company-ispell ()
> > >     (make-local-variable 'company-backends)
> > >     (cond
> > >      (
> > >       (derived-mode-p 'emacs-lisp-mode)
> > >       (setf (alist-get 'company-tabnine company-backends)
> > >             (remove 'company-ispell (alist-get 'company-tabnine
> > > company-backends))))
> > >      (
> > >       t
> > >       (setf (alist-get 'company-tabnine company-backends)
> > >         (append (alist-get 'company-tabnine company-backends)
> > >             '(company-ispell))))))
> > >
> > > (add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)
> >
> > The first cond clause looks good but I don't see why you need the
> > t-clause?  Isn't the thing that company-ispell is part of the default
> > value of the company-tabnine entry of company-backends?  If that's the
> > case, you want to make company-backends buffer-local and remove it in
> > emacs-lisp-mode and derived modes but there is no need to add it again
> > otherwise because the default value won't be altered.  So that'd be:
> >
> > --8<---------------cut here---------------start------------->8---
> > (defun hz/company-tabnine-remove-company-ispell ()
> >   (when (derived-mode-p 'emacs-lisp-mode)
> >     (make-local-variable 'company-backends))
> >     (setf (alist-get 'company-tabnine company-backends)
> >             (remove 'company-ispell
> >                     (alist-get 'company-tabnine company-backends))))
> > --8<---------------cut here---------------end--------------->8---
>
> A very strange result based on the above code is that it will remove
> company-ispell in all modes, say, LaTeX mode. But the following code
> works as expected:
>
> (defun hz/company-tabnine-remove-company-ispell ()
>     (when (derived-mode-p 'emacs-lisp-mode)
>       (setq-local company-backends
>           '((company-tabnine :separate company-capf company-dabbrev
> company-keywords company-files))
>           )))
>
>
> > But most importantly, `emacs-startup-hook' is not the one you want.
> > That runs once after emacs has loaded the init file.  I'm even not sure
> > what buffer is current then.  I guess the most logical hook is
> > `company-mode-hook'.
> >
> >   (add-hook 'company-mode-hook
> >             #'hz/company-tabnine-remove-company-ispell)
>
> This works. Thank you for pointing this out.

The following one, which is based on the idea here [1], also works:

(add-hook 'after-change-major-mode-hook
#'hz/company-tabnine-remove-company-ispell)


[1] https://github.com/hlissner/doom-emacs/blob/0869d28483b5d81b818b110af351fd5c4dc04dd9/modules/completion/company/config.el#L66


> > Or maybe there is also some `company-tabnine-*-hook' that runs after
> > that package has done its setup in a buffer?
>
> Unfortunately, it doesn't supply these type hooks.
>
> HZ



-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province

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

[Hongyi Zhao]

On Thu, Oct 28, 2021 at 12:14 PM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Thu, Oct 28, 2021 at 2:52 AM Tassilo Horn <tsdh@gnu.org> wrote:
> >
> > Hongyi Zhao <hongyi.zhao@gmail.com> writes:
> >
> > >> > However, I can imagine that you might not be able to use it in
> > >> > major-mode hooks such as `emacs-lisp-mode' due to ordering issues,
> > >> > i.e., I can easily imagine that `company-mode' (and this
> > >> > company-tabnine thingy) is initialized *after* the major-mode hook
> > >> > has run because usually, you activate minor-modes in major-mode
> > >> > hooks.  In that case you would try to remove before the
> > >> > company-tabnine entry has been added to company-backends.
> > >> >
> > >> > That's all just guesswork since I don't use company.
> > >>
> > >> [...]
> > >
> > > I also tried the following snippet, but still failed:
> > >
> > > (defun hz/company-tabnine-remove-company-ispell ()
> > >     (make-local-variable 'company-backends)
> > >     (cond
> > >      (
> > >       (derived-mode-p 'emacs-lisp-mode)
> > >       (setf (alist-get 'company-tabnine company-backends)
> > >             (remove 'company-ispell (alist-get 'company-tabnine
> > > company-backends))))
> > >      (
> > >       t
> > >       (setf (alist-get 'company-tabnine company-backends)
> > >         (append (alist-get 'company-tabnine company-backends)
> > >             '(company-ispell))))))
> > >
> > > (add-hook 'emacs-startup-hook #'hz/company-tabnine-remove-company-ispell)
> >
> > The first cond clause looks good but I don't see why you need the
> > t-clause?  Isn't the thing that company-ispell is part of the default
> > value of the company-tabnine entry of company-backends?  If that's the
> > case, you want to make company-backends buffer-local and remove it in
> > emacs-lisp-mode and derived modes but there is no need to add it again
> > otherwise because the default value won't be altered.  So that'd be:
> >
> > --8<---------------cut here---------------start------------->8---
> > (defun hz/company-tabnine-remove-company-ispell ()
> >   (when (derived-mode-p 'emacs-lisp-mode)
> >     (make-local-variable 'company-backends))
> >     (setf (alist-get 'company-tabnine company-backends)
> >             (remove 'company-ispell
> >                     (alist-get 'company-tabnine company-backends))))
> > --8<---------------cut here---------------end--------------->8---
>
> A very strange result based on the above code is that it will remove
> company-ispell in all modes, say, LaTeX mode. But the following code
> works as expected:
>
> (defun hz/company-tabnine-remove-company-ispell ()
>     (when (derived-mode-p 'emacs-lisp-mode)
>       (setq-local company-backends
>           '((company-tabnine :separate company-capf company-dabbrev
> company-keywords company-files))
>           )))

I also obtained the following code snippet, which is extracted from
doom-emacs [1] with slightly adjusting:

```emacs-lisp
;;;;; Some Emacs lisp code extracted from doom-emacs
;;;###autoload
(defvar company-backend-alist
  '((text-mode (company-tabnine :separate company-ispell
company-dabbrev company-yasnippet))
    (prog-mode company-capf company-yasnippet)
    (conf-mode company-capf company-dabbrev-code company-yasnippet))
  "An alist matching modes to company backends. The backends for any mode is
built from this.")

(defun doom-enlist (exp)
  "Return EXP wrapped in a list, or as-is if already a list."
  (declare (pure t) (side-effect-free t))
  (if (proper-list-p exp) exp (list exp)))

;;;###autodef
(defun set-company-backend (modes &rest backends)
  "Prepends BACKENDS (in order) to `company-backends' in MODES.

MODES should be one symbol or a list of them, representing major or minor modes.
This will overwrite backends for MODES on consecutive uses.

If the car of BACKENDS is nil, unset the backends for MODES.

Examples:

  (set-company-backend 'js2-mode
    'company-tide 'company-yasnippet)

  (set-company-backend 'sh-mode
    '(company-shell :with company-yasnippet))

  (set-company-backend '(c-mode c++-mode)
    '(:separate company-irony-c-headers company-irony))

  (set-company-backend 'sh-mode nil)  ; unsets backends for sh-mode"
  (declare (indent defun))
  (dolist (mode (doom-enlist modes))
    (if (null (car backends))
        (setq company-backend-alist
              (delq (assq mode company-backend-alist)
                    company-backend-alist))
      (setf (alist-get mode company-backend-alist)
            backends))))


;;
;;; Library

(defun company--backends ()
  (let (backends)
    (let ((mode major-mode)
          (modes (list major-mode)))
      (while (setq mode (get mode 'derived-mode-parent))
        (push mode modes))
      (dolist (mode modes)
        (dolist (backend (append (cdr (assq mode company-backend-alist))
                                 (default-value 'company-backends)))
          (push backend backends)))
      (delete-dups
       (append (cl-loop for (mode . backends) in company-backend-alist
                        if (or (eq major-mode mode)  ; major modes
                               (and (boundp mode)
                                    (symbol-value mode))) ; minor modes
                        append backends)
               (nreverse backends))))))
```

With the help of the above lisp code, the following configuration is
enough for the question discussed here:

```emacs-lisp
(use-package company-math)

(use-package company-tabnine
  :hook
  (LaTeX-mode . (lambda ()
          (setq-local company-backends (company--backends))
          (add-to-list 'company-backends '(company-math-symbols-latex
                           company-latex-commands))
          ))

  (text-mode . (lambda ()
         (add-to-list 'company-backends 'company-math-symbols-unicode))))
```

But I've two problems with the above method:

1. When the `company--backends' command is used separately, as follows:

(add-hook 'company-mode-hook (lambda ()
                    (setq-local company-backends (company--backends))
                    ))

The `(setq-local company-backends (company--backends))` always put the
default backends set in the `company-backend-alist' at the very
beginning of the ultimate compand-backends result, which makes it
difficult for me to set a higher priority for the company-backends
added in other hooks.

2. The `set-company-backend' command can't  prepend BACKENDS (in
order) to `company-backends' in MODES, say, by the followng one:

  (set-company-backend 'LaTeX-mode
   'company-math-symbols-latex 'company-latex-commands)


[1] https://github.com/hlissner/doom-emacs/blob/develop/modules/completion/company/autoload.el

>
> > But most importantly, `emacs-startup-hook' is not the one you want.
> > That runs once after emacs has loaded the init file.  I'm even not sure
> > what buffer is current then.  I guess the most logical hook is
> > `company-mode-hook'.
> >
> >   (add-hook 'company-mode-hook
> >             #'hz/company-tabnine-remove-company-ispell)
>
> This works. Thank you for pointing this out.
>
> > Or maybe there is also some `company-tabnine-*-hook' that runs after
> > that package has done its setup in a buffer?
>
> Unfortunately, it doesn't supply these type hooks.
>
> HZ