From: "Pascal J. Bourguignon" <pjb@informatimago.com>
To: help-gnu-emacs@gnu.org
Subject: Re: `list-of' macro snippet [regarding Comprehensions]
Date: Wed, 07 Nov 2012 23:30:44 +0100 [thread overview]
Message-ID: <87r4o56o6j.fsf@informatimago.com> (raw)
In-Reply-To: 3445356f-5bb8-4dcd-bd45-d98a4e103a2a@g18g2000vbf.googlegroups.com
Rivka Miller <rivkaumiller@gmail.com> writes:
> I still need someone to help me get the common-lisp comprehension code
> working on emacs.
Require cl and use defmacro* instead of defmacro:
(require 'cl)
(defmacro* comp ((e &rest qs) l2)
(if (null qs) `(cons ,e ,l2) ; rule A
(let ((q1 (car qs))
(q (cdr qs)))
(if (not(eq (cadr q1) '<-)) ; a generator?
`(if ,q1 (comp (,e ,@q),l2) ,l2) ; rule B
(let ((v (car q1)) ; rule C
(l1 (third q1))
(h (gentemp "H-"))
(us (gentemp "US-"))
(us1 (gentemp "US1-")))
`(labels ((,h (,us) ; corresponds to a letrec
(if (null ,us) ,l2
(let ((,v (car ,us))
(,us1 (cdr ,us)))
(comp (,e ,@q) (,h ,us1))))))
(,h ,l1)))))))
(macroexpand '(comp (e (< 1 2)) l2))
--> (if (< 1 2) (comp (e) l2) l2)
(macroexpand '(comp (e) l2))
--> (cons e l2)
--
__Pascal Bourguignon__
http://www.informatimago.com
prev parent reply other threads:[~2012-11-07 22:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <44777946-db62-48fa-9e99-2fd06c6d296c@g18g2000vbf.googlegroups.com>
2012-10-29 0:49 ` `list-of' macro snippet [regarding Comprehensions] Rivka Miller
2012-10-29 2:20 ` Rivka Miller
2012-11-03 2:06 ` Rivka Miller
2012-11-03 3:09 ` Pascal J. Bourguignon
[not found] ` <87pq3vmlg5.fsf@informatimago.com>
2012-11-03 21:57 ` Rivka Miller
2012-11-07 17:08 ` Rivka Miller
2012-11-07 22:30 ` Pascal J. Bourguignon [this message]
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