bug#40671: [DOC] modify literal objects

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Fri, 17 Apr 2020 18:37:23 +0200
> Cc: Kevin Vigouroux <ke.vigouroux@laposte.net>
> 
> > Can we modify literal objects? 
> 
> No, and the manual should do a much better job at explaining this. At the 
> very least it should not promulgate bad ideas by including mutation of 
> literals in example code. Patch attached, suggested for emacs-27.

I don't see any explanation of the issue in the patch, did I miss
something?

What I see summarily replaces literal lists and cons cells with a
calls to functions, and I'm not sure this is a step in the right
direction.  It definitely complicates the examples, which is not
necessarily TRT, methodologically, for such introductory sections.