add-list local value

add-list local value

[Lennart Borgman (gmail)]

Wouldn't it be practical to allow add-list to add to the buffer local 
value, like add-hook allows? At least I need it ...

Re: add-list local value

[Stefan Monnier]

> Wouldn't it be practical to allow add-list to add to the buffer local value,
> like add-hook allows? At least I need it ...

It makes sense for add-hook because buffer-local values of hook include
a special entry t which means "run the global value of this hook".

For lists, it doesn't make much sense I believe.  Either the list is
global or it's local.  If it's local, just make it local with
make-local-variable.


        Stefan

Re: add-list local value

[Lennart Borgman (gmail)]

Stefan Monnier wrote:
>> Wouldn't it be practical to allow add-list to add to the buffer local value,
>> like add-hook allows? At least I need it ...
> 
> It makes sense for add-hook because buffer-local values of hook include
> a special entry t which means "run the global value of this hook".
> 
> For lists, it doesn't make much sense I believe.  Either the list is
> global or it's local.  If it's local, just make it local with
> make-local-variable.


And if I have a local value and want to add to the global value with 
add-to-list?

Re: add-list local value

[Juanma Barranquero]

On Wed, Mar 12, 2008 at 3:18 AM, Lennart Borgman (gmail)
<lennart.borgman@gmail.com> wrote:

>  And if I have a local value and want to add to the global value with
>  add-to-list?

(with-temp-buffer (add-to-list 'my-variable 'my-value))

unless the variable is automatically buffer-local. If it is, I think
it would be uncommon to modify the global value (it would be more
logical to just set it up with defvar), but you can always skip the
`add-to-list' and assign to my-variable with setq-default.

 Juanma

Re: add-list local value

[Lennart Borgman (gmail)]

Juanma Barranquero wrote:
> On Wed, Mar 12, 2008 at 3:18 AM, Lennart Borgman (gmail)
> <lennart.borgman@gmail.com> wrote:
> 
>>  And if I have a local value and want to add to the global value with
>>  add-to-list?
> 
> (with-temp-buffer (add-to-list 'my-variable 'my-value))
> 
> unless the variable is automatically buffer-local. If it is, I think
> it would be uncommon to modify the global value (it would be more
> logical to just set it up with defvar), but you can always skip the
> `add-to-list' and assign to my-variable with setq-default.

Thanks, yes, something like this perhaps

(defun add-to-global-list (list-var element &optional append compare-fn)
   (let ((global-val (default-value list-var)))
     (add-to-list 'global-val element append compare-fn)
     (set-default list-var global-val)))

But I would prefer that add-to-list did it for me.

Re: add-list local value

[Stefan Monnier]

>>> Wouldn't it be practical to allow add-list to add to the buffer local value,
>>> like add-hook allows? At least I need it ...
>> 
>> It makes sense for add-hook because buffer-local values of hook include
>> a special entry t which means "run the global value of this hook".
>> 
>> For lists, it doesn't make much sense I believe.  Either the list is
>> global or it's local.  If it's local, just make it local with
>> make-local-variable.

> And if I have a local value and want to add to the global value with
> add-to-list?

A good reason why add-to-list is a bad function.

You can use

  (require 'cl)

  (pushnew <val> (default-value '<sym>))

or

  (setq-default <sym> (cons <var> (default-value '<sym>)))

or

  (unless (member <val> (default-value '<sym>))
    (setq-default <sym> (cons <var> (default-value '<sym>))))


-- Stefan

Re: add-list local value

[Richard Stallman]

    And if I have a local value and want to add to the global value with 
    add-to-list?

It isn't hard to do this "by hand", and it is rare, so it isn't worth
defining (and documenting!) a new feature.  It would be a change for
the worse.

Emacs is already very complex.  If we added new primitive features
for things like this, it would become far more complex.