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

[Johan Bockgård]

Dieter Wilhelm <dieter@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))

(The whole idea seems a bit ugly though.)

`(substring ... 0 2)' returns a string of length 2, btw.

-- 
Johan Bockgård