Date: Sun, 04 Sep 2016 14:23:35 +0200
From: florian@fsavigny.de (Florian v. Savigny)
Naively, I used the numeric conversion of the prefix arg, i.e.
(interactive "p")
which passes the prefix arg converted to a number. However, if I call
the function with no prefix argument, which is, expectedly, nil in raw
form, it converts this to the number 1. (This is what
`prefix-numeric-value' does, as explained in the docstring.)
While I understand that this is how it is done, I am quite puzzled
about the logic behind this. It would seem intuitive to me to convert
nil to either the number 0 or, again, nil, but never to the number
1. And practically, converting nil to 1 has the consequence that
calling the command with no prefix arg:
M-x command
is exactly the same as calling it with a prefix arg of 1:
C-u 1 M-x command
because the prefix arg converted to a number is 1 in both cases, which
reduces the number of possibilities of calling the command by one.
I can circumvent this (and get the behaviour that I would expect) by
writing the function with
(if current-prefix-arg (prefix-numeric-value current-prefix-arg))
in an explicit interactive list, but I am still wondering about the
rationale of representing nil as the number one. Does this make sense,
or is it useful, in some way?