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Re: Setting the nth element of a list
From: |
Nordlöw |
Subject: |
Re: Setting the nth element of a list |
Date: |
Fri, 5 Jun 2009 06:06:32 -0700 (PDT) |
User-agent: |
G2/1.0 |
On Jun 5, 4:25 am, Barry Margolin <bar...@alum.mit.edu> wrote:
> In article
> <8a7c4d36-195d-4517-827e-7fbeca7ae...@r34g2000vba.googlegroups.com>,
>
> Nordlöw <per.nord...@gmail.com> wrote:
> > This simple example changes the second element in the list x:
>
> > (setq x '(a nil c))
> > (setcar (cdr x 'b)
>
> > How do I generalize this to a function that sets (changes) the nth
> > element of a list (for side effects only)?
>
> > Thanks in advance,
> > Nordlöw
>
> (require 'cl-macs)
> (setf (nth n x) 'b)
>
> --
> Barry Margolin, bar...@alum.mit.edu
> Arlington, MA
> *** PLEASE post questions in newsgroups, not directly to me ***
> *** PLEASE don't copy me on replies, I'll read them in the group ***
Okey, here is my solution:
(defun setnthcar (n list x)
"Set N:th element of LIST to X for side effects only."
(setcar (nthcdr n list) x))
Comments on that?
How do I accomplish the same with arrays? Using aref I guess. Here is
my mockup that doesn't yet do what I want:
(defun setnthref (n array x)
"Set N:th element of ARRAY to X for side effects only."
(set (aref array n) x))
Thanks in advance,
Nordlöw
- Setting the nth element of a list, Nordlöw, 2009/06/04
- RE: Setting the nth element of a list, Drew Adams, 2009/06/04
- Re: Setting the nth element of a list, Lennart Borgman, 2009/06/04
- Re: Setting the nth element of a list, Barry Margolin, 2009/06/04
- Re: Setting the nth element of a list,
Nordlöw <=
- Re: Setting the nth element of a list, Nordlöw, 2009/06/05
- Re: Setting the nth element of a list, Pascal J. Bourguignon, 2009/06/05
- Re: Setting the nth element of a list, Nordlöw, 2009/06/05
- Re: Setting the nth element of a list, Pascal J. Bourguignon, 2009/06/05
- Re: Setting the nth element of a list, bigfaceworm, 2009/06/05
- Re: Setting the nth element of a list, Miles Bader, 2009/06/06
- Re: Setting the nth element of a list, Barry Margolin, 2009/06/05