Re: hooks, again

[Emanuel Berg]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> But as seen earlier, you have to look at the value
> of `foo-hook' before this setq takes place to be
> sure it's safe. So you still need "the help or
> evaluation of the variable name or anything".

Yes, but only once.

> And next time you upgrade Emacs, you'll have to look
> again at the value of `foo-hook' before this setq,
> to make sure your `setq' is still OK.

This never presented a problem and I think it won't
since in my case all this relates to programming mode
hooks and not the more complicated ones that
supposedly would glue together a software package, for
example Gnus. But it is a valid point.

> And nothing explains why you want to remove
> previously present elements from that hook.

And this is nothing I have done either. Usually those
programming mode hooks are empty.

> And of course the above setq doesn't prevent later
> modification of the hook (luckily), so you may still
> need to look at the var's value if you want to know
> what's on the hook.

Indeed, here is some unorthodox use (?) of `add-hook'
and `remove-hook' where I don't want to use `setq',
because that would require first extracting the
original value and then resetting it.

    (defun enable-jump ()
      (add-hook 'w3m-display-hook 'goto-first-hit) )

    (defun goto-first-hit (&optional url)
      (if (search-forward "Top Definition" (point-max) t) ; Urban Dictionary
          (progn
            (forward-line 2)
            (beginning-of-line)
            (recenter-top-bottom 0) )
        (search-forward " 1." (point-max) t)) ; YouTube
      (remove-hook 'w3m-display-hook 'goto-first-hit) )

    (defun web-search ()
      (interactive)
      (let ((search (get-search-string "Google")))
        (unless (empty-string-p search)
          (w3m-new-tab (format "Google: %s" search))
          (w3m-search "google" search) ))
      (enable-jump) ) ; all code [1]

> Normally, you shouldn't need to care what other
> functions are there.

Che Guevara said revolutionaries aren't normal people.
I don't think programmers are either.

> As mentioned before, if you like to use `setq' for
> your hooks, go right ahead. After all, that's how
> add-hook works under the hood. I just strongly
> discourage it and consider it a bug to do that in an
> Elisp package, except for very
> particular circumstances.

The anomaly mentioned was only indirectly the
consequence of `setq'. The hook worked for a single
function when that function was included in a list,
but not if the hook was set to only that function
(quoted). In addition, it was only reported in some
cases (which is why I supplied the code). Just setting
the mode did not result in an error for "non-list"
use. But it all other hooks that I had, for a single,
quoted function (i.e. no list) it worked.

... wait, you mean YOU consider it a bug? Yes, I would
consider it a bug as well in packages because that
could ruin the user's configurations. The idea with
packages are they should float in the air and not ruin
what is below. Agreed.

[1] http://user.it.uu.se/~embe8573/conf/emacs-init/w3m/w3m-unisearch.el

-- 
underground experts united
http://user.it.uu.se/~embe8573