Re: How to populate a property list?

[Hattuari <susudata@setidava.kushan.aa>]

Thien-Thi Nguyen wrote:

> Hattuari <susudata@setidava.kushan.aa> writes:
> 
>> a plist has unique keys
> 
> only if constructed that way.
> 
> consider this *scratch* buffer snapshot:
> 
>   (setq x '(:k1 1 :k2 2 :k1 42))
>   
>   (plist-get x :k1)
>   1
>   
>   (plist-get (cddr x) :k1)
>   42
> 
> here, `(cddr x)' has unique keys, but `x' does not.  both have the plist
> form (i.e., are amenable to passing to `plist-get' or being hung off a
> symbol).  if you use `x' w/ assumption of unique keys, certain usage
> patterns will end up hiding the second :k1 from you but not actually
> recycling it.  result: unsightly (literally!) bloat.  e.g., continuing
> from above:
> 
>   (setplist 'x x)
>   (:k1 1 :k2 2 :k1 42)
> 
>   (get 'x :k1)
>   1
> 
>   (put 'x :k1 "one")
>   "one"
>   
>   (get 'x :k1)
>   "one"
>   
> all's cool from `put' and `get' pov, right?  but the truth is deeper;
> ignorance of it does not make it go away:
> 
>   x
>   (:k1 "one" :k2 2 :k1 42)
> 
> thi

I don't know what to make of this then:

edition 2.9 of the GNU Emacs Lisp Reference Manual, corresponding to GNU
Emacs version 21.3, §8.4.1 Property Lists and Association Lists
------------------------------------------
"Association lists (*note Association Lists::) are very similar to
property lists.  In contrast to association lists, the order of the
pairs in the property list is not significant since the property names
must be distinct."
-- 
p->m == (*p).m == p[0].m