Zsh Mailing List Archive
Messages sorted by:
Reverse Date,
Date,
Thread,
Author
Re: Filtering array on index
- X-seq: zsh-users 23721
- From: Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx>
- To: Jesper Nygårds <jesper.nygards@xxxxxxxxx>
- Subject: Re: Filtering array on index
- Date: Thu, 25 Oct 2018 19:42:22 +0000
- Cc: Zsh Users <zsh-users@xxxxxxx>
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= daniel.shahaf.name; h=message-id:from:to:cc:mime-version :content-transfer-encoding:content-type:references:in-reply-to :date:subject; s=fm1; bh=rL7rMCo8cCuxXIQT6zQIo+vibhBwLZUpIL5E+kg 4rfM=; b=AU2sNI48TseYAihFKx/c+qHgVpBLkpFFbQwPjJAfGfTGDOFLuhHrfa4 cBVZ08AgN1WN8vSXlVLinsaspH/CGhPHU61HyryilkLmzeadQKo+v+g/sdPpiUgA CtN5H2xQE5hKU/of8g75z6FSQ/Jj/fBLljQdDQCUZ/LjuyjrtKwjNKIjFkhHcjBi 6PchqUNRTce7TMYGpoA++uyWEI7FF9M3TsgzD86UGOGLmQAOAMSp2fkR0YfdPwaG QHG7rFCrD1VRqmo6/RLoCfdro6h3Q5H7EJukSl/K1vkcZaMxQbJy0ILQSzAu+ZgR H+NJNv5/8awfhMRc4t8eVGAPqjile2g==
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; bh=rL7rMCo8cCuxXIQT6zQIo+vibhBwLZUpIL5E+kg4r fM=; b=B0FruwyO3rmfV3cPxncFObuqoI6YdbJ96DYrn6HtcOozeJgUnsZFCtIjc vKXUd9D40az0HIiq+/bqRp/uk9NsRGN49kejCqoJYWqeRjvjFH7OvEunaAqVgYW+ FNn55/xt4X1IzJAuHPA1jCIU5S52bRXyp9K+dtmk+8Vg6brJDxFJhZdTm2BWlh+h u0Hf2oHilNTeFLjkI2gFyE79RgZVpjhF1V0BCMduItCT/lqTVLQ2R3eYCETcZmOZ LfSVD0ECBeAJLl9H5XE9bgHsg5bBXI/uoOWMKj2Ss86zOpWQTviHZRwN+sPUcnlv Z2ks4d7Q6mvevNw+Dx+CYpnjbg9AA==
- In-reply-to: <CAHYJk3RTBfnx0KgDO87VCZx=p+QUot_Q57F3F2N+6A7b38ZcHQ@mail.gmail.com>
- List-help: <mailto:zsh-users-help@zsh.org>
- List-id: Zsh Users List <zsh-users.zsh.org>
- List-post: <mailto:zsh-users@zsh.org>
- List-unsubscribe: <mailto:zsh-users-unsubscribe@zsh.org>
- Mailing-list: contact zsh-users-help@xxxxxxx; run by ezmlm
- References: <CABZhJg80vQuMHGKABkzR1bdtt89Akpkfd8kWOV83N-qvqioaXw@mail.gmail.com> <CAHYJk3RTBfnx0KgDO87VCZx=p+QUot_Q57F3F2N+6A7b38ZcHQ@mail.gmail.com>
Mikael Magnusson wrote on Thu, 25 Oct 2018 20:17 +0200:
> On 10/25/18, Jesper Nygårds <jesper.nygards@xxxxxxxxx> wrote:
> > I have an array which is the result of using zparseopts on a specification
> > that makes it possible to specify several filters with a -v flag. The
> > resulting array might look like the following:
> >
> > myarr=(-v filter1 -v filter2)
> >
> > I want to get rid of the "-v" elements, but only when they are the flag,
> > and not the argument. In other words, I would the like the array (-v
> > filter1 -v -v) to result in (filter1 -v).
> >
> > I had previously used:
> >
> > ${myarr:#-v}}
> >
> > which worked well, as I could accept the fact that -v was not possible to
> > use as the option argument.
> >
> > However, now I need to make sure that a -v argument is preserved, and I
> > thus need a compact way of specifying that I want to keep every other
> > element in the array.
> >
> > The most compact way I have found is:
> > for dash arg in $myarr; do myarr[(r)$dash]=()
> >
> > This works, but I was wondering if there's some more elegant solution,
> > preferrably without using iteration?
>
> The above example doesn't work if you need to preserve the order (it
> will just remove the first $dash it finds).
>
> % a=(-v filter1 -v -v -v middle -v -v -v final)
> % for dash arg in $a; do a[(r)$dash]=(); done; pl $a
> filter1
> middle
> -v
> -v
> final
>
> middle "should" be between the two remaining -v.
>
> This works, but is still a loop obviously:
> % for i in {$(($#a/2))..1}; do a[i*2-1]=(); done; pl $a
> filter1
> -v
> middle
> -v
> final
>
> (Note that it is necessary to iterate backwards as the indices will
> change otherwise)
Another option:
myarr=(-v filter1 -v filter2)
() { local i j; myarr=(); for i j; do myarr+=($j) ; done } "${myarr[@]}"
In zparseopts context we can probably assume the arguments to the -v
option don't contain literal NUL bytes, so perhaps something like this:
% myarr=( -v 'foo foo' -v 'bar bar' -v '' )
% printf -v x '\0k1%s\0k2%s\0v' "$myarr[@]"
% x=${x//$'\0k1-v\0k2'}
% x=${x%$'\0v'}
% () { typeset -p argv } "${(@ps.\0v.)x}"
typeset -g -a argv=( 'foo foo' 'bar bar' '' )
%
Is there a way to do this in O(N) time? (The array-based solutions are
quadratic complexity due to indexing/appending being O(N). I'm not sure
about the printf.)
Cheers,
Daniel
Messages sorted by:
Reverse Date,
Date,
Thread,
Author