Re: bug#3688: Also need (auto-fill-mode nil) to trigger this bug

[Kees Bakker <kees.bakker@altium.nl>]

On Monday 29 June 2009, Stefan Monnier wrote:
> > BTW. I never intended to enable auto-fill. But strangly enough the following
> > will _toggle_ auto-fill-mode. (I know, this function is "Toggle Auto Fill mode".
> > Besides a clear description to turn it on, it should also have a clear
> > description to turn it off.)
> 
> >   (auto-fill-mode nil)
> 
> All minor modes are turned on with a positive arg and turned off with
> a negative arg.  A nil argument may toggle it, but that might change in
> the future.  A `toggle' argument toggles most (but not all) minor modes.

OK. I didn't know that (and I'm using emacs for almost two decades now). Still I
want to express my dislike about the way a "nil" arg is handled.

First, is 0 a positive arg? Some people might think so (I do). It is a bit confusing.
(auto-fill-mode 0) will turn the mode off, so in that sense a zero is not a positive
arg. To summarize

   (auto-fill-mode)         ;;; toggles
   (auto-fill-mode 0)       ;;; turn off
   (auto-fill-mode nil)     ;;; toggles
   (auto-fill-mode -1)      ;;; turn off
   (auto-fill-mode 1)       ;;; turn on
   (auto-fill-mode t)       ;;; turn on

Toggling for a "nil" argument does not make sense to me.
-- 
Kees