zsh-workers
 help / color / mirror / code / Atom feed
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



  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAMP44s3NYQA3OSvdEBQ5bNG2O2+w0U3USUvBP7Mi-3urhuKYzg@mail.gmail.com \
    --to=felipe.contreras@gmail.com \
    --cc=schaefer@brasslantern.com \
    --cc=zsh-workers@zsh.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://git.vuxu.org/mirror/zsh/

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).