From: Felipe Contreras <felipe.contreras@gmail.com>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: More rabbit-holes with unset variables
Date: Thu, 26 Nov 2020 19:51:07 -0600 [thread overview]
Message-ID: <CAMP44s3NYQA3OSvdEBQ5bNG2O2+w0U3USUvBP7Mi-3urhuKYzg@mail.gmail.com> (raw)
In-Reply-To: <CAH+w=7Yv1FO4eTSZfTADPJMz++COsFQJ3UKzGbWF4JdCtcV83g@mail.gmail.com>
On Thu, Nov 26, 2020 at 6:23 PM Bart Schaefer <schaefer@brasslantern.com> wrote:
>
> On Thu, Nov 26, 2020 at 3:53 PM Felipe Contreras
> <felipe.contreras@gmail.com> wrote:
> >
> > > There's no way to "see" the export namespace without forking an
> > > external process, so only the internal value matters.
> >
> > No. The exported value exists whether you decide to look at it or not.
>
> The point is that the exported value DOES NOT exist in this example;
> if you were to look at the C global "environ" array following "export
> FOO", it would not have (a pointer to a string containing) "FOO" in
> it.
How do you know?
The example brought by Oliver was this:
export FOO
echo ${FOO-replacement}
How do you know FOO doesn't have a value beforehand?
That's precisely the reason the "-replacement" part is there: FOO may
or may not have a value.
You used precisely this argument when I brought up this example:
func () {
[[ -n "$1" ]] && var=$1
dosomething ${var-other}
}
You said: "It's not possible to write deterministic code."
It is exactly the same thing here.
If we have this example:
[[ -n "${1+set}" ]] && FOO=$1
func () {
export FOO
sh -c 'echo "external: \"${FOO-nil}\""'
echo "internal: \"${FOO-nil}\""
}
func
% sh example.sh bar
external: "bar"
internal: "bar"
All shells I have return the same.
But when I do the same without argument:
% sh example.sh
external: "nil"
internal: "nil"
In all shells, except:
% zsh example.sh
external: "nil"
internal: ""
The inconsistency between the internal and external value *only*
happens in zsh, and it most definitely exists.
> > > > typeset -x FOO
> > > >
> > > > Is different than this:
> > > >
> > > > typeset -x FOO=""
> >
> > If this is not inconsistent, then nothing is.
>
> Now I'm confused. All along you've been arguing that { typeset FOO }
> SHOULD differ from { typeset FOO="" }. Why does adding -x invert your
> argument?
It doesn't.
To be consistent, either these two are the same:
typeset -x FOO
typeset -x FOO=""
Or these two are different:
typeset FOO
typeset FOO=""
As long as in zsh none of these are changed, zsh is objectively
inconsistent. It is *two* inconsistencies.
What I think is obvious should be changed is the latter, so that:
typeset -x FOO
typeset FOO
In both cases FOO is "unset", both locally and externally.
And.
typeset -x FOO=""
typeset FOO=""
In both cases FOO would have an empty string both locally and externally.
I don't see how this *second* inconsistency isn't obvious.
Cheers.
--
Felipe Contreras
next prev parent reply other threads:[~2020-11-27 1:51 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-25 7:02 Bart Schaefer
2020-11-25 13:19 ` Stephane Chazelas
2020-11-25 22:17 ` Felipe Contreras
2020-11-26 6:10 ` Stephane Chazelas
2020-11-26 7:20 ` Felipe Contreras
2020-11-26 11:21 ` Oliver Kiddle
2020-11-26 11:29 ` Roman Perepelitsa
2020-11-26 19:08 ` Felipe Contreras
2020-11-26 19:29 ` Felipe Contreras
2020-11-26 21:13 ` Bart Schaefer
2020-11-26 21:31 ` Felipe Contreras
2020-11-26 23:29 ` Bart Schaefer
2020-11-26 23:32 ` Bart Schaefer
2020-11-26 23:53 ` Felipe Contreras
2020-11-27 0:23 ` Bart Schaefer
2020-11-27 1:51 ` Felipe Contreras [this message]
2020-11-27 20:01 ` Bart Schaefer
2020-11-27 21:49 ` Felipe Contreras
2020-11-27 22:06 ` Bart Schaefer
2020-11-27 23:35 ` Felipe Contreras
2020-11-26 22:07 ` Bart Schaefer
2020-11-26 20:41 ` Bart Schaefer
2020-11-26 20:49 ` Stephane Chazelas
2020-11-26 21:20 ` Felipe Contreras
2020-11-26 22:41 ` Bart Schaefer
2020-11-26 23:45 ` Felipe Contreras
2020-11-27 0:09 ` Bart Schaefer
2020-11-27 0:30 ` Felipe Contreras
2020-11-27 0:51 ` Bart Schaefer
2020-11-27 1:30 ` Felipe Contreras
2020-11-27 20:54 ` Bart Schaefer
2020-11-27 22:10 ` Felipe Contreras
2020-11-27 22:39 ` Bart Schaefer
2020-11-28 0:00 ` Felipe Contreras
2020-11-28 0:04 ` Bart Schaefer
2020-11-28 10:52 ` Felipe Contreras
2020-11-28 0:36 ` The emulation rabbit-hole RE typeset/unset Bart Schaefer
2020-11-28 11:35 ` Felipe Contreras
2020-11-28 16:56 ` Bart Schaefer
2020-12-01 8:49 ` Felipe Contreras
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