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Re: Is there equivalent internal function for this list-has-elements?
From: |
tomas |
Subject: |
Re: Is there equivalent internal function for this list-has-elements? |
Date: |
Sun, 18 Oct 2020 22:58:50 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
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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