From: Thierry Volpiatto <thierry.volpiatto@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: remove-duplicates performances
Date: Fri, 20 May 2011 18:00:40 +0200 [thread overview]
Message-ID: <87pqndcqfr.fsf@gmail.com> (raw)
In-Reply-To: 878vu1qwde.fsf@fencepost.gnu.org
David Kastrup <dak@gnu.org> writes:
> I've found the following in some file of mine:
>
> (defun uniquify (list predicate)
> (let* ((p list) lst (x1 (make-symbol "x1"))
> (x2 (make-symbol "x2")))
> (while p
> (push p lst)
> (setq p (cdr p)))
> ;;; (princ lst)(princ "\n")
> (setq lst
> (sort lst `(lambda(,x1 ,x2)
> (funcall ',predicate (car ,x1) (car ,x2)))))
> ;;; lst now contains all sorted sublists, with equal cars being
> ;;; sorted in order of increasing length (from end of list to start).
> ;;
>
> (while (cdr lst)
> (unless (funcall predicate (car (car lst)) (car (cadr lst)))
> (setcar (car lst) x1))
> (setq lst (cdr lst)))
> (delq x1 list)))
>
> (uniquify '(2 1 2 1 2) '<)
> (uniquify '(4 7 3 26 4 2 6 24 4 5 2 3 2 4 6) '<)
This is nice and very instructive (at least for me) thanks.
It is not as performant as the version with hash-table, but very usable:
0.3 <=> 0.13 with same test on list with 20000 elements.
However, isn't it a problem when we want to remove duplicate in a list
type alist e.g ((a . 1) (b . 2) (a . 1) (c . 3) (b . 2)...)
--
A+ Thierry
Get my Gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 59F29997
next prev parent reply other threads:[~2011-05-20 16:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-20 13:51 remove-duplicates performances Thierry Volpiatto
2011-05-20 14:09 ` Stefan Monnier
2011-05-20 14:39 ` Thierry Volpiatto
2011-05-20 16:14 ` Stefan Monnier
2011-05-20 17:46 ` Thierry Volpiatto
2011-05-20 15:16 ` Ted Zlatanov
2011-05-20 14:28 ` David Kastrup
2011-05-20 16:00 ` Thierry Volpiatto [this message]
2011-05-20 17:01 ` David Kastrup
2011-05-20 17:31 ` Thierry Volpiatto
2011-05-20 17:46 ` David Kastrup
2011-05-20 18:01 ` Stefan Monnier
2011-05-20 21:57 ` Pascal J. Bourguignon
2011-05-20 17:57 ` Ted Zlatanov
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