Re: Check whether an object is an alist

[Heime <heimeborgia@protonmail.com>]

On Tuesday, September 17th, 2024 at 11:23 PM, tomas@tuxteam.de <tomas@tuxteam.de> wrote:

> On Tue, Sep 17, 2024 at 11:16:24AM +0000, Heime wrote:
> 
> > Sent with Proton Mail secure email.
> > 
> > On Tuesday, September 17th, 2024 at 9:46 PM, tomas@tuxteam.de tomas@tuxteam.de wrote:
> > 
> > > On Tue, Sep 17, 2024 at 11:38:46AM +0200, Manuel Giraud via Users list for the GNU Emacs text editor wrote:
> > > 
> > > > Heime heimeborgia@protonmail.com writes:
> > > > 
> > > > > Sent with Proton Mail secure email.
> > > > > 
> > > > > On Monday, September 16th, 2024 at 10:29 PM, Heime heimeborgia@protonmail.com wrote:
> > > > > 
> > > > > > Is there a function that checks whether an object is an alist.
> > > > > > Have only found listp.
> > > > > 
> > > > > Because I may have to come up with a solution, I have made this one.
> > > > > Am I missing anything ?
> > > > > 
> > > > > (defun torium-alist-p (obj)
> > > > > "Return t if object OBJ is an association list (alist)."
> > > > > (and (listp obj)
> > > > > (not (null obj))
> > > > > (every (lambda (x)
> > > > > (and (consp x)
> > > > > (not (null x))))
> > > > > obj)))
> > > > 
> > > > Looks good to me. I think it should `cl-every' instead of` every' and
> > > > also, maybe, nil is a valid empty alist.
> > > 
> > > Unless you'd like to have nil as a possible key (alists allow that,
> > > why not?):
> > > 
> > > (setq al '((nil . "I am not") (t . "I am")))
> > > (alist-get nil al)
> > > => "I am not"
> 
> 
> Oh, wait. I just see you were checking the pair to be not
> null. Then it's easier: your above code seems right, just
> the (not (null x)) is superfluous, since (consp x) makes
> sure it is so.
> 
> Cheers
> --
> t



Have modified the code to this

(defun torium-alist-p (obj)
  "Return t if object OBJ is an association list (alist)."
  (and (listp obj)
       (every (lambda (x)
                (or (null x)
                    (consp x)))
              obj)))

I want to allow empty lists and empty keys.  Or should I remove (null x)
as well ?