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From: Jean Louis <bugs@gnu.support>
To: tomas@tuxteam.de
Cc: help-gnu-emacs@gnu.org
Subject: Re: Is there equivalent internal function for this list-has-elements?
Date: Mon, 19 Oct 2020 21:23:18 +0300	[thread overview]
Message-ID: <20201019182318.GN19325@protected.rcdrun.com> (raw)
In-Reply-To: <20201018205850.GA13219@tuxteam.de>

* tomas@tuxteam.de <tomas@tuxteam.de> [2020-10-18 23:59]:
> On Sun, Oct 18, 2020 at 10:37:01PM +0300, Jean Louis wrote:
> > 
> > For the below function `list-has-elements' maybe there exist some
> > internal Emacs function that checks for list that elements that are
> > contained in the haystak? Is there any?
> > 
> > Other question is, if there is any function other than pushnew, if I
> > do not wish to use the pushnew? I can maybe just make a check if
> > element is in the list and then simply push?
> > 
> > (defun list-has (needle haystack)
> >   "Returns elements of haystack that contain needle, case insensitive"
> >   (let ((nlist))
> >     (dolist (element haystack (reverse nlist))
> >       (when (string-match needle element)
> > 	(pushnew element nlist)))))
> 
> If I understand this one correctly, it can be expressed as:
> 
>   (seq-filter
>     (lambda (elt) (string-match needle elt))
>     haystack)

Thank you, I will use it with string-match-p tip.

> > (defun list-has-elements (needles haystack)
> >   "Returns elements of haystack that contain needle, case insensitive"
> >   (if needles
> >       (let* ((needle (pop needles))
> > 	     (haystack (list-has needle haystack)))
> > 	(list-has-elements needles haystack))
> >     haystack))
> 
> The doc string sent me off to the weeds ;-D

Sorry for that, it was just duplicated badly.

> You want to filter out those elements in haystack which match *all*
> the needles? Then something like (Careful! untested!)
> 
>   (seq-reduce
>     (lambda (red-haystack needle) (list-has needle red-haystack))
>     needles
>     haystack)

That works for now on a small list, I will benchmark it as next to
compare what is faster, as I find those functions very useful.

Thanks,
Jean





      parent reply	other threads:[~2020-10-19 18:23 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-18 19:37 Is there equivalent internal function for this list-has-elements? Jean Louis
2020-10-18 20:43 ` Stefan Monnier
2020-10-19  7:15   ` tomas
     [not found]   ` <20201019180655.GL19325@protected.rcdrun.com>
     [not found]     ` <jwvpn5ef5dx.fsf-monnier+emacs@gnu.org>
2020-10-19 20:15       ` Jean Louis
2020-10-18 20:58 ` tomas
2020-10-18 21:21   ` Joost Kremers
2020-10-19  6:57     ` tomas
2020-10-19 18:08     ` Jean Louis
2020-10-19 18:23   ` Jean Louis [this message]

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