From: "Drew Adams" <drew.adams@oracle.com>
To: "'Wilson Snyder'" <wsnyder@wsnyder.org>, <herring@lanl.gov>
Cc: emacs-devel@gnu.org
Subject: RE: Suggestions to remove one alist's members from another
Date: Fri, 9 Apr 2010 07:45:19 -0700 [thread overview]
Message-ID: <0463395FF50A4311A9738C2EE803FE4F@us.oracle.com> (raw)
In-Reply-To: <20100409141649.833BD18838C@wsnyder.org>
> >> If not, my thought is this: when the list was over some size
> >> I'd determine experimentally, it would instead build a hash
> >> table from in-list and hit the not-alist against that. When
> >> complete it would unfortunately require a second pass
> >> through the in-alist to return it maintaining the original
> >> order.
> >
> >Why not build a hash table (of the cars of the elements)
> >from not-alist instead? Then you can just walk in-alist,
> >skipping elements that are in the hash (that is, whose
> >cars are in it) and adding the rest to out-alist
> >and (their cars to) the hash.
>
> Thanks, that's a good improvement. I also would add each
> in-list element after each test for hash membership, as I
> want to eliminate duplicates.
>
> It still seems like this should already exist somewhere...
Well, there are the `[n]set-difference' sequence functions (in cl-seq.el), but
they're not O(1). You might want to take a look at them anyway.
next prev parent reply other threads:[~2010-04-09 14:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-09 13:02 Suggestions to remove one alist's members from another Wilson Snyder
2010-04-09 14:11 ` Davis Herring
2010-04-09 14:16 ` Wilson Snyder
2010-04-09 14:45 ` Drew Adams [this message]
2010-04-09 14:48 ` Davis Herring
2010-04-09 15:05 ` David Kastrup
2010-04-09 17:31 ` Stephen J. Turnbull
-- strict thread matches above, loose matches on Subject: below --
2010-04-09 12:27 Wilson Snyder
2010-04-09 15:12 ` David Kastrup
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