help with add-to-list syntax

help with add-to-list syntax

[BP25]

Hello! Could any of you be so kind as to help me understand this,
please? I have

(custom-set-variables
'(warning-suppress-types '((undo\ discard-info))))

in my .emacs. If I start emacs, do load-file .emacs, then evaluate
(add-to-list 'warning-suppress-types '(undo\ discard-info)) I get an
error saying the variable warning-suppress-types is void. However if I
start emacs, do load-file .emacs, then do C-h v warning-suppress-types
then I see the value being ((undo\ discard-info)) and if I evaluate
(add-to-list 'warning-suppress-types '(undo\ discard-info)) then
everything goes through without error. Why?!

Please, let me know! (and please, CC: my email address in your reply
because I'm not subscribed to this list)

Re: help with add-to-list syntax

[Michael Heerdegen via Users list for the GNU Emacs text editor]

BP25 <bp25@riseup.net> writes:

> Hello! Could any of you be so kind as to help me understand this,
> please? I have
>
> (custom-set-variables
> '(warning-suppress-types '((undo\ discard-info))))
>
> in my .emacs.

Why is the space character escaped?

> If I start emacs, do load-file .emacs, then evaluate
> (add-to-list 'warning-suppress-types '(undo\ discard-info)) I get an
> error saying the variable warning-suppress-types is void.

You are sure there was no typo involved?

Apart from that I dunno, that makes no sense unless your .emacs messes
up emacs in a crazy way.


Michael.

Re: help with add-to-list syntax

[Joel Reicher]

BP25 <bp25@riseup.net> writes:

> Hello! Could any of you be so kind as to help me understand 
> this, please? I have
>
> (custom-set-variables
> '(warning-suppress-types '((undo\ discard-info))))
>
> in my .emacs. If I start emacs, do load-file .emacs, then 
> evaluate (add-to-list 'warning-suppress-types '(undo\ 
> discard-info)) I get an error saying the variable 
> warning-suppress-types is void.

Instead of doing add-to-list, can you do C-h v and confirm the 
variable setting that you expected didn't work?

That would give a simpler thing to investigate.

Cheers,

        - Joel

Re: help with add-to-list syntax

[BP25]

Hello!

First, the space character should not be escaped, this was my
mistake. But it changes nothing with respect to my problem.

On Wed, Oct 30 2024, Joel Reicher wrote:
>> Hello! Could any of you be so kind as to help me understand this,
>> please? I have
>>
>> (custom-set-variables '(warning-suppress-types '((undo\
>> discard-info))))
>>
>> in my .emacs. If I start emacs, do load-file .emacs, then evaluate
>> (add-to-list 'warning-suppress-types '(undo\ discard-info)) I get an
>> error saying the variable warning-suppress-types is void.
>
> Instead of doing add-to-list, can you do C-h v and confirm the
> variable setting that you expected didn't work?
Do you mean this? -> If I start emacs, do load-file .emacs, then do C-h v
warning-suppress-types then I see the value being ((undo\ discard-info))

Re: help with add-to-list syntax

[Michael Heerdegen]

BP25 <bp25@riseup.net> writes:

> Hello! Could any of you be so kind as to help me understand this,
> please? I have
>
> (custom-set-variables
> '(warning-suppress-types '((undo\ discard-info))))
>
> in my .emacs. If I start emacs, do load-file .emacs, then evaluate
> (add-to-list 'warning-suppress-types '(undo\ discard-info)) I get an
> error saying the variable warning-suppress-types is void.

After thinking about this again:
The explanation for your little miracle is probably that the variable is
autoloaded and the defining library "warnings" not necessarily loaded at
startup.  `custom-set-variables' is clever enough to do the right thing
anyway.  C-h v loads the defining library as a side effect so you always
see a defined variable even when it had not yet been defined.

The details may differ a bit depending on your Emacs version.

Michael.