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Re: 'length' function for lists and cons cells?
From: |
Thorsten Jolitz |
Subject: |
Re: 'length' function for lists and cons cells? |
Date: |
Fri, 22 Mar 2013 03:38:11 +0100 |
User-agent: |
Gnus/5.130002 (Ma Gnus v0.2) Emacs/24.2 (gnu/linux) |
"Pascal J. Bourguignon" <pjb@informatimago.com> writes:
> I don't understand what you want to do.
well, avoid the errors I get when mapping alists with true lists and
cons cells as elements with functions like 'lenght of 'cdr etc.
> You can use length and dolist on alists and it will work perfectly:
> (length '((a . 1) (b . 2) (c . 3)))
> --> 3
yes, but, when mapping the elements:
,------------------------------------------------------------
| (length '(a . 1))
|
| Debugger entered--Lisp error: (wrong-type-argument listp 1)
| length((a . 1))
`------------------------------------------------------------
> (dolist (entry '((a . 1) (b . 2) (c . 3)))
> (destructuring-bind (key . value) entry
> (insert (format "key = %S, value = %S\n" key value))))
> key = a, value = 1
> key = b, value = 2
> key = c, value = 3
I wasn't aware of destructuring-bind, thats cl stuff - had to look it up here:
http://dto.github.com/notebook/require-cl.html#sec-6-6
> If you want to count the cons cells, then why stop at the
> dotted-lists? There are also circular lists. See how you can do it at:
> https://gitorious.org/com-informatimago/com-informatimago/blobs/master/common-lisp/cesarum/list.lisp#line303
ok, thanks for the hint.
--
cheers,
Thorsten
- Re: 'length' function for lists and cons cells?, Pascal J. Bourguignon, 2013/03/21
- Re: 'length' function for lists and cons cells?,
Thorsten Jolitz <=
- Re: 'length' function for lists and cons cells?, Mark Skilbeck, 2013/03/22
- Re: 'length' function for lists and cons cells?, Thorsten Jolitz, 2013/03/22
- Message not available
- Re: 'length' function for lists and cons cells?, Pascal J. Bourguignon, 2013/03/23
- RE: 'length' function for lists and cons cells?, Drew Adams, 2013/03/23
- Message not available
- Re: 'length' function for lists and cons cells?, Pascal J. Bourguignon, 2013/03/23
- RE: 'length' function for lists and cons cells?, Drew Adams, 2013/03/24
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