From: "Stephen J. Turnbull" <stephen@xemacs.org>
To: wsnyder@wsnyder.org (Wilson Snyder)
Cc: emacs-devel@gnu.org
Subject: Re: Suggestions to remove one alist's members from another
Date: Sat, 10 Apr 2010 02:31:02 +0900 [thread overview]
Message-ID: <87vdc04jop.fsf@uwakimon.sk.tsukuba.ac.jp> (raw)
In-Reply-To: <20100409141649.833BD18838C@wsnyder.org>
Wilson Snyder writes:
> >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.
Note that Davis's algorithm already does this, IIUC. Elements that
are just skipped don't need to be added because they are in the hash
already, while elements that are added to the out-alist get added to
the hash, too.
> It still seems like this should already exist somewhere...
The Common Lisp emulation has such operations, but I think they're not
stable.
next prev parent reply other threads:[~2010-04-09 17:31 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
2010-04-09 14:48 ` Davis Herring
2010-04-09 15:05 ` David Kastrup
2010-04-09 17:31 ` Stephen J. Turnbull [this message]
-- 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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