Question

I’ve got a variable in Emacs called my-var that I’d like to set whenever I press C-v. How do I do that? I tried this:

(defun set-my-var (value)   'set my var'   (interactive)   (defvar my-var value     'a variable of mine') )  (global-set-key '\C-v' 'set-my-var) 

But that fails:

call-interactively: Wrong number of arguments: (lambda (value) 'set my var' (interactive) (defvar my-var value 'a variable of mine')), 0 

Answer 1

Actually, defvar doesn’t do what you think it does either: it only changes the value IF there was no value before. Here’s a chunk that does what you’re looking for, using the CTRL-u argument:

(defun set-my-var (value)   'Revised version by Charlie Martin'   (interactive 'p')   (setq my-var value)) 

and here’s an example, code from the *scratch* buffer

(defun set-my-var (value)   'Revised version by Charlie Martin'   (interactive 'p')   (setq my-var value)) ; do ^J to evaluate the defun form, showing return in the buffer. set-my-var  (global-set-key '\C-v' 'set-my-var) set-my-var  ;Another ^J  ;;; Now, what's the value after ^U^V? my-var 4 ;;; Now ^U 8 ^V my-var 8 ;;; now ^U^U^V my-var 16