From: Stephane Chazelas <stephane.chazelas@gmail.com>
To: Sebastian Gniazdowski <sgniazdowski@gmail.com>
Cc: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: [bug] Math evaluation done twice in subscript in specific conditions
Date: Wed, 24 Jul 2019 06:12:34 +0100 [thread overview]
Message-ID: <20190724051234.5yky2pd5pxv5z3lu@chaz.gmail.com> (raw)
In-Reply-To: <CAKc7PVBZa=G0D1v4u9=257O20N85r26HWmjtpxVrNvfoUp-PSQ@mail.gmail.com>
2019-07-24 01:50:23 +0200, Sebastian Gniazdowski:
[...]
> idx=0
> a=()
> : ${a[++idx]::=$idx}
> print -rl $a
> -> 1
> : ${a[++idx]::=$idx}
> print -rl $a
> -> 1
> -> 3
> idx=1
> : ${a[++idx]::=$idx}
> print -rl $a
> -> 1
> -> 2
> -> 3
>
> So apparently the assignment to idx does change something for the
> following ::= "call" and makes it work correctly. The second and
> following ::= calls cause $idx to increment twice.
[...]
It is increased by 2 on the first one as well:
$ i=0 a=()
$ : ${a[++i]::=$i}; echo $i $a
2 1
$ : ${a[++i]::=$i}; echo $i $a
4 1 3
With:
$ i='psvar[0`uname>&2`]'
$ : ${a[i]}
Linux
$ : ${a[i]::=}
Linux
Linux
zsh: a: assignment to invalid subscript range
So the extra evaluation of the indice is done *before* the
assignment it would seem.
$ echo ${a[i]:=x}
Linux
Linux
zsh: a: assignment to invalid subscript range
It makes more sense in that latter case where I imaging a[i] is
dereferenced first to check if it's empty or not, and then the
indice is computed again upon assignment.
--
Stephane
next prev parent reply other threads:[~2019-07-24 5:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 23:50 Sebastian Gniazdowski
2019-07-24 5:12 ` Stephane Chazelas [this message]
2019-07-24 5:33 ` Sebastian Gniazdowski
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