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From: Mikael Magnusson <mikachu@gmail.com>
Date: Fri, 30 Sep 2016 10:28:19 +0200
Message-ID: <CAHYJk3RCgUk+sz=kk-g3qdgHXV9T1FxCQVdiHZcd=AM_U_fwPA@mail.gmail.com>
Subject: Re: Passing array to function
To: Daniel Shahaf <d.s@daniel.shahaf.name>
Cc: Ignatius Reilly <turnbuckle@gmail.com>, Zsh Users <zsh-users@zsh.org>
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On Fri, Sep 30, 2016 at 9:45 AM, Daniel Shahaf <d.s@daniel.shahaf.name> wro=
te:
> Ignatius Reilly wrote on Fri, Sep 30, 2016 at 02:15:55 -0500:
>> addtoarray() { [[ -d $1 ]] && myarray=3D($1 $myarray) }
>>
>> which works as expected, prepending an element to an array only if its a=
n
>> existing directory.  I'd like to rewrite this function so that I can pas=
s
>> the array name as a parameter like so:
>>
>> addtoarray /usr/foo myarray
>
> You could do it with eval:
>
> addtoarray() {
>   [[ -d $1 ]] && eval "${(q)2}[1,0]=3D${(q)1}"
> }
>
> Explanation:
>
> - The (q) are there to convert the values to command-line-quoted
>   strings, for eval.  $2 probably needs no quoting =E2=80=94 if it did, t=
he eval
>   would see a syntax error =E2=80=94 but I put the (q) anyway to guard ag=
ainst
>   invalid inputs (bobby tables attacks against the eval).
>
> - After parameter substitution, the resultant string is:
>     myarray[1,0]=3D/usr/foo
>   which is a slice assignment that prepends an element to the named
>   array.
>
> If there's a solution without eval I'm sure someone will post it.

addtoarray() { [[ -d $1 ]] || return; local p=3D"$2[1,0]"; : ${(P)p::=3D$1}=
 }
I forgot about [1,0] yesterday when you asked on IRC.

--=20
Mikael Magnusson