Re: Appending lists

[tomas]

On Wed, Jun 16, 2021 at 08:36:00PM +0300, Jean Louis wrote:
> * Philip Kaludercic <philipk@posteo.net> [2021-06-16 16:07]:
> > > (setq list '(A B C)) ⇒ (A B C)
> > > (nconc list '(1 2 3)) ⇒ (A B C 1 2 3)
> > > list  ⇒ (A B C 1 2 3)
> > 
> > Change that to
> > 
> (let* ((list-1 '(a b c))
>         (list-2 (nconc list-1 '(1 2 3))))
                   ^^^^ not recommended: '(a b c) is a "constant object"
                        Some version of elisp might even refuse to do that!
>    (eq list-1 list-2)) ;; => t
> 
> eq - Return t if the two args are the same Lisp object.
> 
> And we talked how variable's value does not change... values or Lisp
> objects?
> 
> (setq list-1 '(a b c))
> list-1 ⇒ (a b c)
> (setq list-2 (nconc list-1 '(1 2 3))) ⇒ (a b c 1 2 3)
> list-2 ⇒ (a b c 1 2 3)
> (eq list-1 list-2) ⇒ t
> list-1 ⇒ (a b c 1 2 3)
> 
> How I see that is that it is same lisp object, but I can visually see
> that the value changed. 
> 
> Maybe Thomas wanted to say that lisp object does not change? 

On the contrary. Mutable objects can change. Cons cells are
mutable objects, and thus lists, which are made of those.

Cheers
 - t

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