comp.lang.lisp Google Group

Re: declaring 'ignore' inside a loop using destructuring

t...@cley.com (Tim Bradshaw) — Tue, 24 Nov 2009 20:47:37 UT

I think it is, probably, not an implementation issue, but I am not sure.
For DOTIMES (for instance) it is explicitly undefined whether each
variable is rebound for each iteration or whether there is only one
binding per variable. This means it is undefined whether the variable
is ignored or not if you do not use it. Simplifying to the point of

Re: Remembering information during compilation

spi...@gmail.com (Spiros Bousbouras) — Tue, 24 Nov 2009 19:23:19 UT

On Sun, 22 Nov 2009 14:14:25 +0100
Pascal Costanza <p...@p-cos.net> posted:
But since you're not explaining what "side effects" means in the context
of Lisp you're not really imparting any information.
Indeed. By using the full power of Lisp for writing macros (or anything
else) I make sure that my programming will be as quick and enjoyable as

Re: Remembering information during compilation

spi...@gmail.com (Spiros Bousbouras) — Tue, 24 Nov 2009 18:54:09 UT

On Sat, 21 Nov 2009 09:42:45 -0800 (PST)
I'm not writing a macroexpand-all function. The possibility occurred to
me and I considered starting a thread on the subject (and I may still
do) but I imagine it cannot be done portably. I was simply saying that
it would be convenient if the standard included a macroexpand-all

Re: Circular slot/member reference when defining class

p...@informatimago.com (Pascal J. Bourguignon) — Tue, 24 Nov 2009 18:43:47 UT

Remove the line:
:type dir-tree-widget
you don't earn anything really with it.
(defclass a ()
((b :initarg :b :accessor a-b)))
(defclass b ()
((a :initarg :a :accessor b-a)))
(defmethod print-object ((self a) stream)
(print-unreadable-object (self stream :identity t :type t)
(write `(:b ,(a-b self)) :circle t :stream stream))

Re: declaring 'ignore' inside a loop using destructuring

russell_mcma...@yahoo.com — Tue, 24 Nov 2009 17:34:25 UT

Perhaps the obvious?
(defun foo (some-list)
(loop for (a b c) in some-list
do b
(print a) (print c)))
-russ

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Re: Circular slot/member reference when defining class

es...@vestre.net (Espen Vestre) — Tue, 24 Nov 2009 17:23:28 UT

Hmm. On the extremely rare occasions where I've needed something
like this, I think I've just defined a dummy version of the class
first. I.e.:
(defclass a ()
;; dummy version, completely empty
())
(defclass b ()
;; real version
(..fill inn stuff here..))
(defclass a ()
;; real version
(..fill inn stuff here..))

Re: declaring 'ignore' inside a loop using destructuring

kyle...@gmail.com (Kyle M) — Tue, 24 Nov 2009 17:22:08 UT

I like the destructuring in loop. That's one reason I use it so much.
I'm parsing a CSV file with several fields, so my code looks like
(loop for newline = (read-line is nil)
while newline
as (quarterback halfback fullback ...other stuff... )
= (delimited-string-to-list newline #\,) ;;allegro CL

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Re: declaring 'ignore' inside a loop using destructuring

kentil...@gmail.com (Kenneth Tilton) — Tue, 24 Nov 2009 17:08:22 UT

It is /so/ C++! But this is loop, which is a DSL for iteration meaning
they went nuts for productivity and had fun with syntax as needed to
keep the productivity up.
If you don't like it, don't use it. Do not try to come up with a better
way, this is Lisp, you won't.
Hunh? Did someone leave you in a strait jacket so you can't reach the

Circular slot/member reference when defining class

jrw...@gmail.com (jrwats) — Tue, 24 Nov 2009 17:01:37 UT

So in C++ when class A needs a pointer to class B and likewise class B
needs the same you just do:
// A.h
class B;
class A {
//...
B* pb;
// B.h
class A;
class B {
//...
A* pa;
How do we accomplish the same in Common Lisp? I'd rather not take the
types out of the class definitions here...

Re: declaring 'ignore' inside a loop using destructuring

kyle...@gmail.com (Kyle M) — Tue, 24 Nov 2009 15:00:54 UT

Thanks. That helps, although I'm a little annoyed by that.
Partially because it looks weird. Although most of my code looks
weird, so that's not a huge deal.
Also, though, because I will wind up using the variable b at some
point later on, and I'd like to give it a name (a descriptive name,
not just b).

Re: declaring 'ignore' inside a loop using destructuring

kentil...@gmail.com (Kenneth Tilton) — Tue, 24 Nov 2009 14:33:29 UT

It's kinda weird:
(loop for (a nil c)....
Same as for destructuring-bind, btw.
kt

declaring 'ignore' inside a loop using destructuring

kyle...@gmail.com (Kyle M) — Tue, 24 Nov 2009 14:28:38 UT

Here's a question for the loopers. Say I'm using loop destructuring
like this:
(defun foo (some-list)
(loop for (a b c) in some-list
do ;; code that uses a and c, but not b:
(print a) (print c)))
(compile 'foo) -> Warning: Variable b is never used.
I know that in a destructuring-bind or a multivalue-bind you can just

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