Re: [O] [RFC] Change some defcustoms into defcont

[Carsten Dominik]

Dear Nicolas,

On Oct 21, 2013, at 5:15 PM, Nicolas Goaziou <address@hidden> wrote:

> Carsten Dominik <address@hidden> writes:
> 
>> The documentation of defconst says:
>> 
>>> Define SYMBOL as a constant variable.
>>> This declares that neither programs nor users should ever change the
>>> value.  This constancy is not actually enforced by Emacs Lisp, but
>>> SYMBOL is marked as a special variable so that it is never lexically
>>> bound.
>> 
>> So it is pretty clear about the intent of such a definition, which is
>> to never change it - even though it does not enforce it.
> 
> I must have been clear as mud, because that's exactly what I'm
> suggesting since the beginning of this thread: set "DEADLINE" and al. in
> stone, and never change them again.

You also said things like

> That's exactly the point of the defconst: you can still modify the
> variable, but it sends a strong message to the user. Also, it's not
> about deprecation: code base should still rely on these variables.

so maybe I picked one interpretation over the other.

> 
> I have been pointing out, though, that it would not break previous
> changes if they were done with `setq', according to how defconst are
> handled. But I never intended to make it a feature, nor did I suggest
> that was desirable.
> 
>> As you have said, we still want to allow users in principle to change
>> these variables.
> 
> No, I haven't said such a thing. I said, verbatim, "In principle, they
> mustn't be changed", which means quite the contrary.
> 
>> They have been defcustoms in the past, some people will have changed
>> them. Their setup will break when they switch to a new version.
> 
> Indeed. But that's easy to fix programmatically.
> 
>> That is why I object to changing their status. I think it causes
>> unnecessary breakage, and we can prevent this by keeping them
>> defcustom. Nothing is really gained by changing their status.
> 
> It fixes at least a bug, prevents headaches by simplifying maintenance,
> makes Org syntax more portable and more cache friendly. I wouldn't call
> that "nothing".

Yes, sorry.   By "nothing" I mean nothing we cannot achieve with documentation
and a :set method.  Since we will still rely on the variables, the advantage for
maintenance is something I do not see.  Cache friendliness I see, but I would 
think
that if someone changes these variables, they will not keep changing them.

> 
> Anyway, I have well understood that you don't want to change their
> status. So be it.

OK, thank you.

Regards

- Carsten