Re: Appending lists

[Jean Louis]

* Yuri Khan <yuri.v.khan@gmail.com> [2021-06-16 14:18]:
> On Wed, 16 Jun 2021 at 16:35, Jean Louis <bugs@gnu.support> wrote:
> 
> > What is it doing in background, or underground, does not really matter
> > for user, what matters is that `x' in following example is changed:
> 
> See, that’s your problem: You think there *is* an underground.
> 
> Lisp starts with symbols and cons cells and that’s the ground level.
> It then builds up from that to lists and trees and associative lists.
> And when you have an associative list binding a symbol to a value,
> that’s when you get variables, some three floors above the ground.

That is why I leave that to engineers like you. You see, today my
friend was mentioning how he does not like one but the other webmail
system. He has no clue about the underlying software, what he wants it
functionality. 

> And then, when you invoke ‘nreverse’ on a list pointed to by a
> variable, you, from high up above, can see it scurrying down there and
> re-routing the ‘cdr’s of the cons cells comprising the list, but not
> touching the one link from the variable to whatever cons cell had been
> the first in the list.

I like your smartness, though I would like to have more practical use
of it. Thomas said that `nconc' does not change `list', unless it is
special form. And I can practically see this:

(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)

So maybe he was thinking that symbol `list' does not change, and I
understood it that variable value does not change.

Why not come back to that and explain me how the variable `list' did
not change from (A B C) to (A B C 1 2 3)?


-- 
Jean

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