Re: Printing an alist of plists with cons format

On Tuesday, March 24th, 2026 at 1:39 AM, Stefan Monnier via Users list
for the GNU Emacs text editor <[email protected]> wrote:

> >> ((:cm :10pt 283.46456 :pt 28.34646 :mm 10 :in 0.3937 :ft 0.03281)
> >>  (:in :10pt 720 :pt 72 :mm 25.4 :cm 2.54 :ft 0.083333)
> >>  (:ft :10pt 8640 :pt 864 :mm 304.8 :cm 30.48 :in 12))
> >>
> >
> > That's a list of lists, not really an alist.  Try improving the code above
> > to produce this form:
> >
> > ((:cm (:10pt 283.46456 :pt 28.34646 :mm 10 :in 0.3937 :ft 0.03281))
> >  (:in (:10pt 720 :pt 72 :mm 25.4 :cm 2.54 :ft 0.083333))
> >  (:ft (:10pt 8640 :pt 864 :mm 304.8 :cm 30.48 :in 12)))))
>
> I disagree.  The first above is an "alist of plists" while the
> alternative you propose would be an "alist of (singleton) lists of
> plists".


> E.g. `(alist-get :in ...)` would return
>
>     (:10pt 720 :pt 72 :mm 25.4 :cm 2.54 :ft 0.083333)
>
> for the first and
>
>     ((:10pt 720 :pt 72 :mm 25.4 :cm 2.54 :ft 0.083333))
>
> for the second
>
> === Stefan


I am still failing to transfer the level-two plist as an entity
as the second element of each cons cell. 

(defun mpl-plist-to-alist (plist)
  "Convert a nested two-level plist (:u1 plist1 :u2 plist2 ...)
to an alist at top-level '((u1 . plist1) (u2 . plist2) ...)."

  (let ( (alist nil)
         (tail  plist))
    (while tail
      (let ( (unit  (car tail))
             (mltp  (cadr tail)) )
        (push (cons unit mltp) alist)
	(setq tail (cddr tail))))
    (nreverse alist)))