Re: Evaluation of hooks

[Sebastian Tennant]

Sebastian Tennant <sebyte@smolny.plus.com> wrote:

> Tom Breton <tehom@REMOVEpanNOSPAMix.com> wrote:
>
>> Sebastian Tennant <sebyte@smolny.plus.com> wrote:
>> 
>>> Hi all,
>>> 
>>> I would like to add a function to my emacs-lisp-mode-hook so that whenever
>>> I visit emacs source files, view-mode minor mode is enabled.
>>> 
>>>   (add-hook 'emacs-lisp-mode-hook
>>>       (lambda ()
>>>         (when (>= (compare-strings
>>>                (buffer-file-name) 1 nil "/usr/share/emacs/" 1 nil) 17)
>>>           (view-mode-enable))))
>>> 
>>> With the above code in my ~/.emacs, I get the following message at startup:
>>> 
>>>   >=: Wrong type argument: stringp, nil
>> 
>> I doubt that has anything to do with hooks.
>
> It's odd though, don't you think?  I'm wondering if I should fie a bug report.
>
>>> but apart from this the startup process is unaffected, and the function is
>>> successfully added to my emacs-lisp-mode-hook, as you can see:
>>> 
>>> ((lambda nil
>>>    (when
>>>        (>
>>>     (compare-strings
>>>      (buffer-file-name)
>>>      0 nil "/usr/share/emacs/" 0 nil)
>>>     18)
>>>      (view-mode-enable))))
>> 
>> Nope, that doesn't work either ... sometimes.
>
> I've got it working (despite the aforementioned error at startup). The problem
> was that (view-mode-enable) is only defined as a function *after* view-mode is
> loaded.  The fix was to replace this with (view-mode 1).

And I've now realised why I'm getting the error at startup.  As we all know, a
*scratch* buffer is created by default at startup and is by definition not
visitng a file.  This is what was causing the problem.

Adding the following line before the (when ...) condition fixes this and the
hook is now functioning perfectly.

  (unless (not (buffer-file-name))
    ...)

sdt