Re: How to detect C-u supplied arguments from other prefix arguments

[Barry Margolin]

In article <1186576048.530383.47680@q75g2000hsh.googlegroups.com>,
 dieter.wilhelm@googlemail.com wrote:

> On 8 ao?t, 13:55, bojohan+n...@dd.chalmers.se (Johan Bockg?rd) wrote:
> > Dieter Wilhelm <die...@duenenhof-wilhelm.de> writes:
> > > I'd like to detect whether prefix arguments of a command are supplied
> > > by C-u or otherwise.
> >
> > > My idea is to use this-command-keys and compare it to some string,
> > > like the following pseudo code:
> >
> > > (defun bla (arg)
> > >   (interactive "p")
> > >   (when (string= "C-u" (substring (this-command-keys) 0 2))
> > >     (message "hurray")))
> >
> > > I just don't understand how to compare key sequences.
> >
> > You want to check for the character ^U, not the three-character string
> > `C - u'. Like
> >
> >     (eq ?\C-u (aref (this-command-keys) 0))
> 
> hurray it works, thanks a lot!
> >
> > (The whole idea seems a bit ugly though.)
> 
> Why?  In Emacs there are just too little short key combinations free.
> I'd like to achieve
> a switch for certain functions depending whether their arguments ARG
> are supplied by C-u or not.
> 
> For example: M-d might kill ARG word with the following boundary/
> whitespace or without,
> or C-t might drag a character ARG chars away and in the other case
> merely transpose neighbouring chars some ARG chars away.

And what if the user decides to bind a different keystroke to 
universal-argument?

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
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