bug#40671: [DOC] modify literal objects

[Paul Eggert]

On 4/19/20 3:24 PM, Drew Adams wrote:
> Don't say "constant".  Say "don't try to change it".

That's too long and awkward a phrase for use in lots of places around the 
manual. We need a simple noun phrase to describe the concept; this is 
Documentation 101.

One possible substitute is "literal object", as Mattias pointed out. Another 
possibility is "immutable object". Perhaps others might be better.

> The only cases that are problematic are those where
> you can think your code modifies something (anew)
> when in fact it might not.

No, that's not the only issue. If you modify some of these "constants" (or 
"literal objects" or whatever term you like), the behavior is undefined: Emacs 
can crash or remove your home directory or whatever. There is no checking.
> By mischaracterizing not mutable as "should not be
> changed" (instead of "cannot be changed"), you can
> give the false impression that the opposite is true:
> if something is mutable then there's no reason you
> shouldn't change it.

I don't see that false impression being given. But if it is being given, 
presumably the problem could be fixed by appropriate wording changes. Specific 
suggestions welcome.