remove-hook creates a symbol if it doesn't exist

remove-hook creates a symbol if it doesn't exist

[Seb]

Hi,

The function remove-hook creates a symbol if its HOOK arg doesn't exist
as such:

(remove-hook 'non-existent-hook 'some-function)


,-----[ C-h v non-existent-hook RET ]
| non-existent-hook's value is nil
| 
| Documentation:
| Not documented as a variable.
| 
| [back]
`-----


Cheers,

-- 
Seb

Re: remove-hook creates a symbol if it doesn't exist

[Stefan Monnier]

> The function remove-hook creates a symbol if its HOOK arg doesn't exist
> as such:

> (remove-hook 'non-existent-hook 'some-function)


> ,-----[ C-h v non-existent-hook RET ]
> | non-existent-hook's value is nil
> | 
> | Documentation:
> | Not documented as a variable.
> | 
> | [back]
> `-----

Indeed.  Any other piece of trivia you want to share with us?


        Stefan


PS: I don't consider the above as a bug.

Re: remove-hook creates a symbol if it doesn't exist

[Kevin Rodgers]

Seb wrote:
> Hi,
> 
> The function remove-hook creates a symbol if its HOOK arg doesn't exist
> as such:
> 
> (remove-hook 'non-existent-hook 'some-function)
> 
> 
> ,-----[ C-h v non-existent-hook RET ]
> | non-existent-hook's value is nil
> | 
> | Documentation:
> | Not documented as a variable.
> | 
> | [back]
> `-----

Actually, the read function interned the symbol.

-- 
Kevin Rodgers
Denver, Colorado, USA

RE: remove-hook creates a symbol if it doesn't exist

[Drew Adams]

> > The function remove-hook creates a symbol if its HOOK arg 
> > doesn't exist as such:
> > 
> > (remove-hook 'non-existent-hook 'some-function)
> > 
> > ,-----[ C-h v non-existent-hook RET ]
> > | non-existent-hook's value is nil
> > | 
> > | Documentation:
> > | Not documented as a variable.
> > | 
> > | [back]
> > `-----
> 
> Actually, the read function interned the symbol.

`read', on its own, doesn't assign a value. It interns a name, creating a
symbol, but it doesn't give it a nil value.

Re: remove-hook creates a symbol if it doesn't exist

[Kevin Rodgers]

Drew Adams wrote:
>>> The function remove-hook creates a symbol if its HOOK arg 
>>> doesn't exist as such:
>>>
>>> (remove-hook 'non-existent-hook 'some-function)
>>>
>>> ,-----[ C-h v non-existent-hook RET ]
>>> | non-existent-hook's value is nil
>>> | 
>>> | Documentation:
>>> | Not documented as a variable.
>>> | 
>>> | [back]
>>> `-----
>> Actually, the read function interned the symbol.
> 
> `read', on its own, doesn't assign a value. It interns a name, creating a
> symbol, but it doesn't give it a nil value.

Good point.  So I tried to replicate the OP's error in Emacs 22.3, but:

emacs -Q --eval "(progn (remove-hook 'non-existent-hook 'some-function) 
non-existant-hook)"

results in this error:

Symbol's value as variable is void: non-existant-hook

And:

emacs -Q --eval "(progn (remove-hook 'non-existent-hook 'some-function) 
(describe-variable 'non-existant-hook))"

results in this *Help* buffer:

non-existant-hook is void as a variable.


Documentation:
Not documented as a variable.


-- 
Kevin Rodgers
Denver, Colorado, USA