Dude where is my car ?

Philippe M. Coatmeur

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May 25, 2012, 6:59:10 PM5/25/12

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Hi everyone ;

I have this function that loops trough a list of lists of email
elements to extract them. The list looks like this :

(("<te...@adamweb.net>" "Fri, 25 May 2012 23:49:58 +0200" "Re: plopz" "1648")
("contact <pl...@gmail.com>" "Fri, 25 May 2012 22:21:49 +0000" "tst" "1647"))

(This is what you get if you C-h v with point over mail-bug-unseen-mails-one)

(defun mail-bug-desktop-notify-one ()
(mapcar
(lambda (x)
(if (not (member x mail-bug-advertised-mails-one))
(progn
(mail-bug-desktop-notification
"Mew mail!"
(format "%s %s %s" ;; Produces the values below
(car (nthcdr 1 x)) ;; Fri, 25 May 2012 23:49:58 +0200
(car (nthcdr 2 x)) ;; Re: plopz
(car (nthcdr 3 x))) ;; 1648
"500000" mail-bug-new-mail-icon-one)
(add-to-list 'mail-bug-advertised-mails-one x))))
mail-bug-unseen-mails-one))

And this works fine, so it follows that (car (car x)) is the first
element of each atomic list, right ? but when I try to extract it
emacs (24.1.50 cvs) insults me!? I spent more than a good hour trying
to figure this out

(format "%s %s %s"
(car (car x)) ;; Should produce <te...@adamweb.net>
(car (nthcdr 2 x)) ;; Re: encor un autre
(car (nthcdr 3 x))) ;; 1643

error in process sentinel: format: Wrong type argument: listp, "<te...@adamweb.net>"
error in process sentinel: Wrong type argument: listp, "<te...@adamweb.net>"

(How am I supposed to interpret this first error ? Does format really
expect a list?) What is it that I'm doing wrong ? Where is my car?

Phil

Eric Abrahamsen

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May 25, 2012, 10:51:26 PM5/25/12

to help-gn...@gnu.org

Since x equals ("<te...@adamweb.net>" "Fri, 25 May 2012 23:49:58 +0200"
"Re: plopz" "1648") in your second example, the car of that is
"<te...@adamweb.net>", and you can't take the car of that again, because
it fails to pass the listp test. I think where you're going wrong is
that nthcdr returns a list, so you can car it. Car itself returns an
atom, so you can't.

Have I got that right?

Also, the whole thing might be easier to read/debug if you use "first"
"second" "third" "fourth" to extract the list elements. Or, if that
seems too unscientific, then "nth", that also pulls a single element out
of a list.

Eric

--
GNU Emacs 24.1.50.1 (i686-pc-linux-gnu, GTK+ Version 2.24.10)
of 2012-05-25 on pellet

Stefan Monnier

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May 26, 2012, 10:04:45 AM5/26/12

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> (car (nthcdr 1 x)) ;; Fri, 25 May 2012 23:49:58 +0200
> (car (nthcdr 2 x)) ;; Re: plopz
> (car (nthcdr 3 x))) ;; 1648

Aka:
(nth 1 x) ;; Fri, 25 May 2012 23:49:58 +0200
(nth 2 x) ;; Re: plopz
(nth 3 x)) ;; 1648

-- Stefan

Philippe M. Coatmeur

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May 26, 2012, 3:00:48 PM5/26/12

to help-gn...@gnu.org

At Sat, 26 May 2012 10:51:26 +0800,

Eric Abrahamsen wrote:
> Since x equals ("<te...@adamweb.net>" "Fri, 25 May 2012 23:49:58 +0200"
> "Re: plopz" "1648") in your second example, the car of that is
> "<te...@adamweb.net>", and you can't take the car of that again, because
> it fails to pass the listp test. I think where you're going wrong is
> that nthcdr returns a list, so you can car it. Car itself returns an
> atom, so you can't.
>
> Have I got that right?
>
> Also, the whole thing might be easier to read/debug if you use "first"
> "second" "third" "fourth" to extract the list elements. Or, if that
> seems too unscientific, then "nth", that also pulls a single element out
> of a list.
>
> Eric

I did now know of those "first, second, etc" things, thanks. Turns out
I had to send the vars as such and then do the format at the last
stage of the text processing, witch makes sense. Thanks for your
patience.

Philippe