Re: plist structure

On Tuesday, March 24th, 2026 at 12:12 PM, [email protected] <[email protected]> wrote:

> Heime <[email protected]> writes:
> 
> > Consider this property list
> >
> > '(:10pt 283.46456 :pt 28.34646 :mm 10 :in 0.3937 :ft 0.03281)
> >
> > It looks like a normal list to be, with elements next to each other.
> >
> > What determines whether a list is a normal list or a plist?  Is it
> > just the parsing routines that read the same list differently (e.g.
> > with plist-get)?
> >
> 
> In Emacs Lisp, the function ‘plistp’ determines whether a
> list is a property list.
> 
> (plistp (list 'a 'b))
> ;;=> t
> (plistp (list 'a 'b 'c))
> ;;=> nil
> (plistp (list 'a 'b 'c 9))
> ;;=> t
> 
> See more in the Emacs Lisp reference manual: (info "(elisp) Property Lists")

Right.  This is basically a matter of interpretation, if plistp determines that
the list is a plist if there are even number of elements.

I have done a few more tests

The following gave me :cm

(car '(:cm (:10pt 283.46456 :pt 28.34646 :mm 10 :in 0.39370 :ft 0.03281)
       :in (:10pt 720 :pt 72 :mm 25.4 :cm 2.54 :ft 0.083333)))

And this

(cdr '(:cm (:10pt 283.46456 :pt 28.34646 :mm 10 :in 0.39370 :ft 0.03281)
       :in (:10pt 720 :pt 72 :mm 25.4 :cm 2.54 :ft 0.083333)))

gave 

((: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))

But then plist-get considers the structure as key val key val ...


 
> --
> The lyf so short, the craft so long to lerne.
> - Geoffrey Chaucer, The Parliament of Birds.