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Re: cons* and append!
From: |
Andreas Rottmann |
Subject: |
Re: cons* and append! |
Date: |
Fri, 13 Feb 2004 21:05:00 +0100 |
User-agent: |
Gnus/5.1006 (Gnus v5.10.6) Emacs/21.3 (gnu/linux) |
Brian S McQueen <address@hidden> writes:
> I few weeks back I asked abit about list building and I got some helpful
> responses. The operator cons* was recommended to me. Well I noticed
> append! yesterday. Does anyone have any comments on this? It seems an
> excellent way of extending proper lists without copying or reallocating
> elements, since it merely clobbers the trailing null list of one list and
> inserts the car of the appended list in its place. Are there some hidden
> expenses I am unaware of? Does it have to walk the entire length of the
> first list to find the end?
>
Yes, append! will have to walk all the lists but the last. All you
save is copying them.
Andy
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