Move to other window backwards?

Question

Emacs has the function other-window that lets you jump between windows. The function's documentation states that it takes an optional argument that tells the function how many windows to jump ahead.

Once upon a time, I defined a keyboard shortcut to call (other-window -1) to jump to the previous window. But at some point (GNU Emacs 25, I think), this stopped working. At first, it did not bother me much, but over time it has become a real nuisance. So if anybody knows a way to replicate that behavior, I would be very grateful!

The function I wrote looks like this:

(defun previous-window ()
    (interactive nil)
    (other-window -1))

And it is bound to a command key like so:

(global-set-key "\C-xp" 'previous-window)

The error message I get:

other-window: Wrong number of arguments: (lambda nil (interactive nil) (other-window -1)), 3

When I run emacs -Q and enter the function and keybinding manually, I get the same error.

Also, I have a function to switch to the previous frame:

(defun prev-frame ()
    (interactive nil)
    (other-frame -1))

This function works as expected.

Answer 1

The problem is the function previous-window does already exist and is called by other-window. You can get info about it with C-h f previous-window (before you define your own previous-window):

previous-window is a built-in function in ‘C source code’.

(previous-window &optional WINDOW MINIBUF ALL-FRAMES)

...

So the fix is simply to call your own function some other name.

(defun myprevious-window ()
    (interactive)
    (other-window -1))

Note: it turns out there is also a function previous-frame so your second function would fail in the same way if you call it previous-frame instead of prev-frame.