Subject: bug#13835: closed (Re: bug#13835: [PATCH] Let reverse! accept arbitrary types as second argument (new_tail))

From: [email-masked] (GNU bug Tracking System)
Date: Thu, 28 Feb 2013 01:53:02 +0000

Your bug report

#13835: [PATCH] Let reverse! accept arbitrary types as second argument (new_tail)

which was filed against the guile package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
13835: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13835
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#13835: [PATCH] Let reverse! accept arbitrary types as second argument (new_tail)
From: Mark H Weaver <[email-masked]>
To: David Kastrup <[email-masked]>
Cc: [email-masked]
Date: Wed, 27 Feb 2013 20:50:24 -0500
List-Id: <debbugs-submit.debbugs.gnu.org>

David Kastrup <[email-masked]> writes:
> There is no reason to restrict the type of the second argument to proper
> lists as it is added as last CDR to the list without interpretation.
>
> This allows for stack-depth friendly usage [...]

Looks good to me.  Applied, thanks!

    Mark

Subject: [PATCH] Let reverse! accept arbitrary types as second argument (new_tail)
From: David Kastrup <[email-masked]>
To: [email-masked]
Cc: David Kastrup <[email-masked]>
Date: Wed, 27 Feb 2013 16:37:21 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

There is no reason to restrict the type of the second argument to proper
lists as it is added as last CDR to the list without interpretation.

This allows for stack-depth friendly usage (simplified from an actual
use case that blew up around my ears) like

SCM
my_tree_copy (SCM src)
{
  if (scm_is_pair (src))
    {
      SCM res = SCM_EOL;
      do
        {
          res = scm_cons (my_tree_copy (scm_car (src)), res);
          src = scm_cdr (src);
        }
      while (scm_is_pair (src));
      return scm_reverse_x (res, my_tree_copy (src));
    }
  return src;
}

* libguile/list.c (scm_reverse_x): remove typecheck for 2nd arg
---
 libguile/list.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/libguile/list.c b/libguile/list.c
index 6c8f8be..d30f9e8 100644
--- a/libguile/list.c
+++ b/libguile/list.c
@@ -377,8 +377,6 @@ SCM_DEFINE (scm_reverse_x, "reverse!", 1, 1, 0,
   SCM_VALIDATE_LIST (1, lst);
   if (SCM_UNBNDP (new_tail))
     new_tail = SCM_EOL;
-  else
-    SCM_VALIDATE_LIST (2, new_tail);
 
   while (!SCM_NULL_OR_NIL_P (lst))
     {
-- 
1.7.10.4