more than one prefix argument

["Andreas Röhler" <andreas.roehler@easy-emacs.de>]

Hi,

what about allowing more than one prefix argument
by making interactive codes "p" and "P" sending
truly separated.

Would reserve "p" for numerical args, while "P"
basically should send a kind of exception flag,
branching execution.

Below a use-case for it, yank-repeat should add
newlines if C-u follows the numeric argument.

As both inputs interfere, that's not possible that way
for now.

;; not working now
(defun yank-repeat-newline (arg &optional nl)
   "With numerical ARG, repeat last yank ARG times.
With optional arg NL, also insert newlines. "
   (interactive "p\nP*")
   (let ((nl nl)
         (num arg))
     (dotimes (i num)
       (if nl
           (insert (concat (car kill-ring) "\n"))
         (insert (car kill-ring))))))


Drew presented a solution at help-gnu-emacs@gnu.org:

;;;;;;;;;;;;;;;;;

As Teemu explained, there is only _one_ prefix arg. You can look at 
either its
numeric value or its raw value or both, but there is only ONE prefix arg.

You apparently want to have a prefix arg express both a numeric quantity 
and a
boolean.  If the user uses C-u (or its variants) to specify a (non-nil) 
prefix
arg then, well, the raw value is non-nil.  If the raw value is nil, then the
user did not use C-u (or its variants).

If you want to let the user specify a numeric value, default 1, and also 
specify
whether to add a newline, then one way to do that is to distinguish positive
from negative prefix arg (there's your boolean).

E.g.:

M-x yank...    -> just one, no newline
M-- yank...    -> one, newline
C-u -1 yank... -> one, newline
C-u -2 yank... -> two, newlines
C-u  2 yank... -> two, no newlines

Something like this:

(defun myyank (&optional arg)
   (interactive "p")
   (dotimes (i (abs arg))
     (if (natnump arg)
	(insert (car kill-ring))
       (insert (concat (car kill-ring) "\n")))))

;;;;;;;;;;;;;

However, that solution seems too complicated for a
part of non-programmers, it's not mnemonic, rather
tricky - even not uncommon in Emacs.

Would be glad to have C-u as general branch key.

Thanks all,

Andreas

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