bug#56799: (gnu services configuration) usage of *unspecified* is problematic

[Tobias Geerinckx-Rice via Bug reports for GNU Guix <bug-guix@gnu.org>]

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Hi Maxim,

Maxim Cournoyer 写道：
> For some background reading, see [0].

Thanks for the well-thought-out reply, and sharing this 
interesting link!

Now, it's just the musings of one person, but now I think I do 
agree with (what I think is) the underlying vision: to hush up 
*unspecified* and sneakily replace it with true nothingness.  OK, 
I can live with that.  :-)

> I think the semantic of the language is that it is to be used as 
> the
> lack of a return value from a procedure or syntax, e.g.:
>
> (unspecified? (if #f 'one-arm-if)) -> #t

Well… in the above context I'd hesitate to even imply ‘semantics’. 
It's like undefined behaviour in C.  Ascribe it meaning at your 
peril.  Otherwise, point taken.

> Having 'unspecified?' even defined in Guile seems to go against 
> that
> idea; perhaps because Wingo themselves seems to disagree in [0].

Agreed.  *This* was one of my reasons for supporting (field 
*unspecified*), so it's nice to have it validated, even if it is 
rejected.

> I'm also thinking 'unspecified being too close to *unspecified* 
> is
> probably going to cause confusion down the line.  Reverting to 
> the
> originally used 'disabled may be the lesser evil.

Ah, here I can concentrate all my previous disagreement: hell no 
:-)

It is the worstest evil; literally anything is better than 
(enable-foo? 'disabled) defaulting to #t.

Bikeshed this all y'all want, but 'default or 'unset or 'whatever 
are miles better.

Kind regards,

T G-R

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