From: Stephane Chazelas <stephane@chazelas.org>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: Oliver Kiddle <opk@zsh.org>, Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: [PATCH 1/3]: Add named references
Date: Sun, 11 Feb 2024 07:00:42 +0000 [thread overview]
Message-ID: <20240211070042.4j37hkgjjn3dfjqd@chazelas.org> (raw)
In-Reply-To: <CAH+w=7aKwKhdXjPo2FQG1GqjHQzX=5to_m6kZeL-UFfQh_XMtw@mail.gmail.com>
2023-02-10 23:45:36 -0800, Bart Schaefer:
[...]
> A named parameter declared with the '-n' option to any of the 'typeset'
> commands becomes a reference to a parameter in scope at the time of
> assignment to the named reference, which may be at a different call
> level than the declaring function. For this reason, it is good practice
> to declare a named reference as soon as the referent parameter is in
> scope, and as early as possible in the function if the reference is to a
> parameter in a calling scope.
[...]
One difference with ksh93: if the target variable was not set at
the time of the "typeset -n ref=target", then when ref is
assigned it may end up refering to a local target:
$ ./Src/zsh -c 'function f { typeset -n ref=$1; typeset var=foo; ref=X; echo "$ref ${(!)ref} $var"; }; f var; echo "$var"'
X var X
$ ./Src/zsh --emulate ksh -c 'function f { typeset -n ref=$1; typeset var=foo; ref=X; echo "$ref ${!ref} $var"; }; f var; echo "$var"'
X var X
$
Compare with ksh:
$ ksh -c 'function f { typeset -n ref=$1; typeset var=foo; ref=X; echo "$ref ${!ref} $var"; }; f var; echo "$var"'
X var foo
X
That's a common use case like for the zslurp function discussed
on zsh-users where one would do:
cmd | zslurp var
To get the output of cmd verbatim into $var with $var potentially undeclared
beforehand, which wouldn't work if var was used locally by zslurp.
It can be worked around with a typeset -g $1 before the typeset -n var=$1
$ ./Src/zsh --emulate ksh -c 'function f { typeset -g $1; typeset -n ref=$1; typeset var=foo; ref=X; echo "$ref ${!ref} $var"; }; f var; echo "$var"'
X var foo
X
But it seems to me it would be better to align with ksh's
behaviour in this instance.
--
Stephane
next prev parent reply other threads:[~2024-02-11 7:01 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-06 2:21 Bart Schaefer
2023-02-08 3:45 ` Oliver Kiddle
2023-02-08 4:59 ` Bart Schaefer
2023-02-08 23:16 ` Bart Schaefer
2023-02-09 0:47 ` Oliver Kiddle
2023-02-09 2:01 ` Oliver Kiddle
2023-02-09 5:45 ` Bart Schaefer
2023-02-09 4:49 ` Bart Schaefer
2023-02-09 20:49 ` Oliver Kiddle
2023-02-09 23:07 ` Bart Schaefer
2023-02-11 3:04 ` Bart Schaefer
2023-02-11 3:55 ` Bart Schaefer
2023-02-11 5:36 ` Speaking of dangerous referents Bart Schaefer
2023-02-12 8:00 ` Oliver Kiddle
2023-02-12 8:34 ` Bart Schaefer
2023-02-11 7:02 ` [PATCH 1/3]: Add named references Oliver Kiddle
2023-02-11 7:45 ` Bart Schaefer
2023-02-11 23:43 ` Bart Schaefer
2023-02-11 23:45 ` Bart Schaefer
2023-02-12 7:38 ` Oliver Kiddle
2024-02-11 7:00 ` Stephane Chazelas [this message]
2024-02-11 16:14 ` Bart Schaefer
2024-02-11 16:42 ` Bart Schaefer
2024-02-18 3:26 ` Up-scope named references, vs. ksh Bart Schaefer
2024-02-20 21:05 ` Stephane Chazelas
2024-02-20 22:30 ` Bart Schaefer
2024-02-21 20:12 ` Stephane Chazelas
2024-02-29 5:16 ` Bart Schaefer
2024-03-01 18:22 ` Stephane Chazelas
2024-03-01 20:34 ` Bart Schaefer
2024-03-02 7:29 ` Bart Schaefer
2024-03-02 23:55 ` [PATCH] "typeset -nu" (was Re: Up-scope named references, vs. ksh) Bart Schaefer
2024-03-01 23:28 ` Up-scope named references, vs. ksh Bart Schaefer
2024-03-03 13:44 ` Stephane Chazelas
2024-03-03 19:04 ` Bart Schaefer
2024-03-03 20:27 ` Stephane Chazelas
2024-03-03 22:58 ` Bart Schaefer
2024-03-04 19:59 ` Stephane Chazelas
2024-03-05 1:05 ` Oliver Kiddle
2024-03-05 2:53 ` Bart Schaefer
2024-03-05 5:43 ` Mikael Magnusson
2024-03-05 6:30 ` Stephane Chazelas
2024-03-06 5:04 ` [PATCH] local vs. nameref scoping (was Re: Up-scope named references, vs. ksh) Bart Schaefer
2023-02-12 9:02 ` [PATCH 1/3]: Add named references Oliver Kiddle
2023-02-12 18:59 ` Bart Schaefer
2023-02-12 19:45 ` PM_* flags in zsh.h (was Re: [PATCH 1/3]: Add named references) Bart Schaefer
2023-02-12 21:01 ` Oliver Kiddle
2023-02-12 22:54 ` [PATCH 1/3]: Add named references Oliver Kiddle
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=20240211070042.4j37hkgjjn3dfjqd@chazelas.org \
--to=stephane@chazelas.org \
--cc=opk@zsh.org \
--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).