* list versus apply
@ 2005-04-20 22:22 Kevin Ryde
2005-04-22 23:45 ` Kevin Ryde
2005-06-05 17:30 ` Marius Vollmer
0 siblings, 2 replies; 6+ messages in thread
From: Kevin Ryde @ 2005-04-20 22:22 UTC (permalink / raw)
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Looks like list doesn't produce a new list when called through apply,
(define x '(1 2 3))
(define y (apply list x))
(eq? x y)
=> #t
I'm looking at the fix below. This removes the C level scm_list, but
that should be ok, it's not documented and does nothing.
[-- Attachment #2: list.c.list.diff --]
[-- Type: text/plain, Size: 791 bytes --]
--- list.c.~1.58.2.7.~ 2004-05-02 07:19:23.000000000 +1000
+++ list.c 2005-04-20 16:31:40.725063792 +1000
@@ -117,17 +117,6 @@
}
-SCM_DEFINE (scm_list, "list", 0, 0, 1,
- (SCM objs),
- "Return a list containing @var{objs}, the arguments to\n"
- "@code{list}.")
-#define FUNC_NAME s_scm_list
-{
- return objs;
-}
-#undef FUNC_NAME
-
-
#if (SCM_DEBUG_DEPRECATED == 0)
SCM_REGISTER_PROC (s_list_star, "list*", 1, 0, 1, scm_cons_star);
@@ -547,6 +536,13 @@
}
#undef FUNC_NAME
+
+SCM_PROC (s_list, "list", 0, 0, 1, scm_list_copy);
+SCM_SNARF_DOCS (register, scm_list_copy, "list", (SCM objs), 0, 0, 1,
+ "Return a list containing @var{objs}, the arguments to\n"
+ "@code{list}.")
+
+
\f
/* membership tests (memq, memv, etc.) */
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: list versus apply
2005-04-20 22:22 list versus apply Kevin Ryde
@ 2005-04-22 23:45 ` Kevin Ryde
2005-06-05 17:30 ` Marius Vollmer
1 sibling, 0 replies; 6+ messages in thread
From: Kevin Ryde @ 2005-04-22 23:45 UTC (permalink / raw)
I wrote:
>
> (define x '(1 2 3))
> (define y (apply list x))
> (eq? x y)
> => #t
Actually, I see in the head this happens under the debugging evaluator
but not the normal one. I made my change because it fixes a bug in
1.6 and the head, but maybe there's something fishy between debug and
normal in the head.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: list versus apply
2005-04-20 22:22 list versus apply Kevin Ryde
2005-04-22 23:45 ` Kevin Ryde
@ 2005-06-05 17:30 ` Marius Vollmer
2005-06-05 20:37 ` Kevin Ryde
1 sibling, 1 reply; 6+ messages in thread
From: Marius Vollmer @ 2005-06-05 17:30 UTC (permalink / raw)
Kevin Ryde <user42@zip.com.au> writes:
> Looks like list doesn't produce a new list when called through apply,
>
> (define x '(1 2 3))
> (define y (apply list x))
> (eq? x y)
> => #t
Is it required to make a copy in this situation? I thought that
(define (list . args) args)
is an acceptable definition of list. Is it not?
--
GPG: D5D4E405 - 2F9B BCCC 8527 692A 04E3 331E FAF8 226A D5D4 E405
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: list versus apply
2005-06-05 17:30 ` Marius Vollmer
@ 2005-06-05 20:37 ` Kevin Ryde
2005-06-05 21:11 ` Marius Vollmer
0 siblings, 1 reply; 6+ messages in thread
From: Kevin Ryde @ 2005-06-05 20:37 UTC (permalink / raw)
Cc: guile-devel
Marius Vollmer <mvo@zagadka.de> writes:
>
> (define (list . args) args)
>
> is an acceptable definition of list. Is it not?
Yep, because args is of course a fresh list when calling a lambda, but
it looks like primitives (C code) aren't called with a copied list
like that.
(I guess having primitives like that makes some sense, only a few are
interested in modifying or re-using their input "rest" list.)
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: list versus apply
2005-06-05 20:37 ` Kevin Ryde
@ 2005-06-05 21:11 ` Marius Vollmer
2005-06-05 21:21 ` Kevin Ryde
0 siblings, 1 reply; 6+ messages in thread
From: Marius Vollmer @ 2005-06-05 21:11 UTC (permalink / raw)
Kevin Ryde <user42@zip.com.au> writes:
> Marius Vollmer <mvo@zagadka.de> writes:
>>
>> (define (list . args) args)
>>
>> is an acceptable definition of list. Is it not?
>
> Yep, because args is of course a fresh list when calling a lambda, but
> it looks like primitives (C code) aren't called with a copied list
> like that.
Ahh, I see. R5RS says: "The value stored in the binding of the last
variable will be a newly allocated list of the actual arguments..." I
think I was confusing this with Common Lisp, which says: "The value of
a rest parameter is permitted, but not required, to share structure
with the last argument to apply."
> (I guess having primitives like that makes some sense, only a few are
> interested in modifying or re-using their input "rest" list.)
We need to document this difference between Scheme functions and C
primitives, I'd say.
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^ permalink raw reply [flat|nested] 6+ messages in thread
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2005-04-20 22:22 list versus apply Kevin Ryde
2005-04-22 23:45 ` Kevin Ryde
2005-06-05 17:30 ` Marius Vollmer
2005-06-05 20:37 ` Kevin Ryde
2005-06-05 21:11 ` Marius Vollmer
2005-06-05 21:21 ` Kevin Ryde
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