`make-local-variable' and `add-hook'

`make-local-variable' and `add-hook'

[Sebastian P. Luque]

Hi,

Is this the best way to give a buffer-local value to a variable inside a
hook:

---<---------------cut here---------------start-------------->---
(add-hook 'sql-interactive-mode-hook
	  (lambda ()
	    (setq sql-input-ring-file-name "~/.emacs.d/sql_history")
	    (set (make-local-variable 'truncate-lines) t)))
---<---------------cut here---------------end---------------->---

?  I'm a bit confused about the last paragraph in the docs:

,-----[ C-h f make-local-variable RET ]
| make-local-variable is an interactive built-in function in `C source code'.
| 
| 
| (make-local-variable variable)
| 
| Make variable have a separate value in the current buffer.
| Other buffers will continue to share a common default value.
| (The buffer-local value of variable starts out as the same value
| variable previously had.  If variable was void, it remains void.)
| Return variable.
| 
| If the variable is already arranged to become local when set,
| this function causes a local value to exist for this buffer,
| just as setting the variable would do.
| 
| This function returns variable, and therefore
|   (set (make-local-variable 'variable) VALUE-EXP)
| works.
| 
| See also `make-variable-buffer-local'.
| 
| Do not use `make-local-variable' to make a hook variable buffer-local.
| Instead, use `add-hook' and specify t for the LOCAL argument.
`-----


Cheers,

-- 
Seb

Re: `make-local-variable' and `add-hook'

[Reiner Steib]

On Wed, Apr 02 2008, Sebastian P. Luque wrote:

> Is this the best way to give a buffer-local value to a variable inside a
> hook:
>
> ---<---------------cut here---------------start-------------->---
> (add-hook 'sql-interactive-mode-hook
> 	  (lambda ()
> 	    (setq sql-input-ring-file-name "~/.emacs.d/sql_history")
> 	    (set (make-local-variable 'truncate-lines) t)))

`truncate-lines' is already buffer-local:

,----[ <f1> v truncate-lines RET ]
| truncate-lines is a variable defined in `C source code'.
| Its value is nil
| 
| Automatically becomes buffer-local when set in any fashion.
`----

> ---<---------------cut here---------------end---------------->---
>
> ?  I'm a bit confused about the last paragraph in the docs:
>
> ,-----[ C-h f make-local-variable RET ]
[...]
> | Do not use `make-local-variable' to make a hook variable buffer-local.
> | Instead, use `add-hook' and specify t for the LOCAL argument.
> `-----

This paragraph would be relevant if you'd like to make
`sql-interactive-mode-hook' buffer-local.

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/