Re: shuffle array

[Stephane Chazelas <stephane.chazelas@gmail.com>]

2019-12-01 23:38:48 +0000, Daniel Shahaf:
[...]
> I think the following would work? —
> 
>     typeset -a l=(…)
>     eval "l=(" $(print -rl -- "${(@qqqq)l}" | shuf) ")"
> 
> shuf(1) expects newline-separated output, and the output of ${(qqqq)} never
> has literal newlines.

$(...) should be quoted or there'll be IFS-splitting.

I wouldn't trust qqqq with eval in locales using charsets like
BIG5, BIG5-HKSCS, GB18030...

$ LC_ALL=zh_HK.big5hkscs luit
$ l=('α')
$ eval "print -r -- $(printf '%s\n' "${(@qqqq)l}")"
zsh: unmatched '

In pratice, I think only ${(q)...} (using single quotes) is
totally safe for reinput regardless of the locale (at least with
the locales typically available on GNU systems).

So you'd want to do something like:

(){ local LC_ALL=C
  eval "l=($(printf '%s\n' "${(@qqqq)l}" | shuf))"
}

That "eval" would still make me nervous.

The:

l=(/(Ne['reply=("$l[@]")']oe['REPLY=$RANDOM']))

approach I gave would not have this kind of issue and would
avoid the dependency on a GNU utility. (it's got its own issues
linked to zsh's $RANDOM taking only 32768 different values, or
being easy to guess...).

-- 
Stephane