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Re: Basic questions about elisp


From: David Kastrup
Subject: Re: Basic questions about elisp
Date: Tue, 10 Nov 2009 19:53:35 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux)

Francis Moreau <address@hidden> writes:

> On Nov 10, 1:11 pm, Joost Kremers <address@hidden> wrote:
>> Francis Moreau wrote:
>> > address@hidden (Pascal J. Bourguignon) writes:
>> >> Well, there are several places where it's covered, but here is one
>> >> where it's explicitely explained:
>>
>> >> (info "(elisp)Rearrangement")
>> [...]
>>
>> > ok that tells: "don't do that !" but it doesn't tell why not...
>>
>> just imagine a list as an object living somewhere in the memory of
>> your computer. then try to figure out which list gets *modified* by
>> the call to nconc, keeping in mind that nconc does *not* copy its
>> arguments before doing its job.
>
> I don't really want to imagine some scenarios when reading this kind
> of documentation.
>
> BTW, the documentation is actually taking about the non-last argument,
> however I was using a constant list for the last argument. So it
> wouldn't apply in my case...

In the second iteration, your constant list has become part of the first
argument.

-- 
David Kastrup


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