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bug#26540: 25.2; [PATCH] Add cl-set-equal to test for set equality
From: |
Damien Cassou |
Subject: |
bug#26540: 25.2; [PATCH] Add cl-set-equal to test for set equality |
Date: |
Wed, 03 May 2017 15:12:05 +0200 |
Hi Michael,
Michael Heerdegen <michael_heerdegen@web.de> 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.
I agree with you that having :key would be nice. Nevertheless, my
implementation currently relies on functions of seq.el (i.e.,
seq-contains) which would have to be adapted to support :key. I
didn't want to do that.
[...] 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
as far as I can tell, little effort has been put in optimizing
seq.el the way you describe it so I guess such an implementation
of seq-set-equal would feel a bit alien in the current code
base. Moreover, is your implementation faster on very small sets?
Finally, making your implementation of seq-set-equal accepting a
TESTFN parameter would be a bit complex as you would have to pass
that to `make-hash-table` which also requires a hash function.
--
Damien Cassou
http://damiencassou.seasidehosting.st
"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill