* list conversion
@ 2003-05-06 19:46 Z. Huang
2003-05-06 20:04 ` Barry Margolin
2003-05-06 20:09 ` Jesper Harder
0 siblings, 2 replies; 4+ messages in thread
From: Z. Huang @ 2003-05-06 19:46 UTC (permalink / raw)
Given a list ("first" "second" "third"). I'd to convert it to a
a new list:
(("" . "first")
("" . "second")
("" . "third"))
The following lisp code was intended for this purpose, but not working. It
looks that I missed some very basic stuff (I rarely code in lisp). Can
anyone point out what is wrong? Thanks in advance.
(defun list-conversion (arg)
(let ((l arg) (new-list ()))
(while l
(append new-list (list "" . (car l))))
(setq l (cdr l))))
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: list conversion
2003-05-06 19:46 list conversion Z. Huang
@ 2003-05-06 20:04 ` Barry Margolin
2003-05-06 20:09 ` Jesper Harder
1 sibling, 0 replies; 4+ messages in thread
From: Barry Margolin @ 2003-05-06 20:04 UTC (permalink / raw)
In article <yq0cznlz26za.fsf@blinky.bloomberg.com>,
Z. Huang <zghuang@bloomberg.net> wrote:
>(defun list-conversion (arg)
> (let ((l arg) (new-list ()))
> (while l
> (append new-list (list "" . (car l))))
> (setq l (cdr l))))
(defun list-conversion (list)
(mapcar '(lambda (item) (cons "" item)) list))
Here's a version more like your original attempt:
(defun list-conversion (list)
(let ((l arg) (new-list '()))
(while l
(setq new-list (cons (cons "" (car l))))
(setq l (cdr l)))
(nreverse new-list)))
Note that you need to re-assign new-list each time through the loop; append
creates a new list, but it doesn't change what new-list refers to. Also,
you need to use cons, not list, to create something of the form (x . y).
--
Barry Margolin, barry.margolin@level3.com
Genuity Managed Services, a Level(3) Company, Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: list conversion
2003-05-06 19:46 list conversion Z. Huang
2003-05-06 20:04 ` Barry Margolin
@ 2003-05-06 20:09 ` Jesper Harder
1 sibling, 0 replies; 4+ messages in thread
From: Jesper Harder @ 2003-05-06 20:09 UTC (permalink / raw)
zghuang@bloomberg.net (Z. Huang) writes:
> Given a list ("first" "second" "third"). I'd to convert it to a
> a new list:
> (("" . "first")
> ("" . "second")
> ("" . "third"))
>
> The following lisp code was intended for this purpose, but not working. It
> looks that I missed some very basic stuff (I rarely code in lisp). Can
> anyone point out what is wrong? Thanks in advance.
You could do it like this:
(defun list-conversion (list)
(mapcar (lambda (x) (cons "" x)) list))
^ permalink raw reply [flat|nested] 4+ messages in thread
* list conversion
@ 2003-05-06 19:33 Zhengao. Huang
0 siblings, 0 replies; 4+ messages in thread
From: Zhengao. Huang @ 2003-05-06 19:33 UTC (permalink / raw)
Given a list ("first" "second" "third"), I'd like to transfrom it into the
a new list:
(("" . "first")
("" . "second")
("" . "third"))
The following lisp code was intended for this purpose, but not working. It
looks that I missed some very basic stuff (I rarely code in lisp). Can
anyone point out what is wrong? Thanks in advance.
(defun list-conversion (arg)
(let ((l arg) (new-list ()))
(while l
(append new-list (list "" . (car l))))
(setq l (cdr l))))
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2003-05-06 20:09 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2003-05-06 19:46 list conversion Z. Huang
2003-05-06 20:04 ` Barry Margolin
2003-05-06 20:09 ` Jesper Harder
-- strict thread matches above, loose matches on Subject: below --
2003-05-06 19:33 Zhengao. Huang
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).