From: <tomas@tuxteam.de>
To: help-gnu-emacs@gnu.org
Subject: Re: Is there equivalent internal function for this list-has-elements?
Date: Sun, 18 Oct 2020 22:58:50 +0200 [thread overview]
Message-ID: <20201018205850.GA13219@tuxteam.de> (raw)
In-Reply-To: <courier.000000005F8C9961.0000177E@static.rcdrun.com>
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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)
> (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
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)
See elisp manual "6.1 Sequences"
All untested.
Cheers
- t
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next prev parent reply other threads:[~2020-10-18 20:58 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 [this message]
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
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