Re: same data appears twice, interactive then function body

[Jean Louis]

* Emanuel Berg via Users list for the GNU Emacs text editor 
<help-gnu-emacs@gnu.org> [2020-12-16 07:03]:
> Stefan Monnier wrote:
> 
> > Here's my take on it:
> >
> >     (defun insert-string-centered (string &optional width)
> >       (interactive
> >        (list (read-from-minibuffer "string: ")
> >              (string-to-number (read-from-minibuffer "width [80]: "))) )
> >       (let*((max         (if (< 0 width) width (+ 42 42 -4)))
> >     [...]
> >
> > Now the question is how to avoid having 42 appear twice,
> > I guess

I remember from micro computers that we used division in this way
to find the center.

(defun insert-centered-text (text &optional width)
  (interactive "MText: ")
  (let* ((width (or width (window-text-width)))
         (length (length (string-trim text)))
         (pos (/ (- width length) 2)))
    (move-to-column pos t)
    (insert text)
    (insert "\n")))