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bug#26540: 25.2; [PATCH] Add cl-set-equal to test for set equality
From: |
Michael Heerdegen |
Subject: |
bug#26540: 25.2; [PATCH] Add cl-set-equal to test for set equality |
Date: |
Wed, 19 Apr 2017 23:19:03 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) |
Damien Cassou <damien@cassou.me> writes:
> Damien Cassou <damien@cassou.me> writes:
> > it makes sense and I will try this way. Nevertheless, it also means
> > giving up on the :key feature. I guess it's ok.
OTOH I see no reason not to support it. There is no reason to provide a
function in a library specializing on sequences with less features than
in some other lib. Just my personal opinion. Of course you can get the
effect of :key by adopting the TESTFN, but also note my other comment:
> here it is. Any feedback?
It might be worth it to try to optimize things a bit for the most usual
TESTFNs `eq' and `equal'. For example, try
#+begin_src emacs-lisp
(let ((s1 (number-sequence 1 10000))
(s2 (number-sequence 1 10000)))
(seq-set-equal s1 s2))
#+end_src
vs.
#+begin_src emacs-lisp
(let ((s1 (number-sequence 1 10000))
(s2 (number-sequence 1 10000)))
(seq-set-equal-2 s1 s2))
#+end_src
with this implementation using hash-tables:
#+begin_src emacs-lisp
(defun seq-set-equal-2 (sequence1 sequence2)
(let ((table1 (make-hash-table :size (length sequence1)))
(table2 (make-hash-table :size (length sequence2))))
(seq-doseq (elt sequence1) (puthash elt t table1))
(seq-doseq (elt sequence2) (puthash elt t table2))
(and (seq-every-p (lambda (elt) (gethash elt table2)) sequence1)
(seq-every-p (lambda (elt) (gethash elt table1)) sequence2))))
#+end_src
I guess other functions in seq.el could be optimized as well,
e.g. `seq-difference'.
Regards,
Michael.
- bug#26540: 25.2; [PATCH] Add cl-set-equal to test for set equality, (continued)
bug#26540: 25.2; [PATCH] Add cl-set-equal to test for set equality, John Mastro, 2017/04/18