(alist-copy): Rewrite in C.

srfi/srfi-1.c

@@ -63,6 +63,40 @@ equal_trampoline (SCM proc, SCM arg1, SCM arg2)
 }
 
 
+SCM_DEFINE (scm_srfi1_alist_copy, "alist-copy", 1, 0, 0,
+            (SCM alist),
+	    "Return a copy of @var{alist}, copying both the pairs comprising\n"
+	    "the list and those making the associations.")
+#define FUNC_NAME s_scm_srfi1_alist_copy
+{
+  SCM  ret, *p, elem, c;
+
+  /* ret is the list to return.  p is where to append to it, initially &ret
+     then SCM_CDRLOC of the last pair.  */
+  ret = SCM_EOL;
+  p = &ret;
+
+  for ( ; scm_is_pair (alist); alist = SCM_CDR (alist))
+    {
+      elem = SCM_CAR (alist);
+
+      /* each element of alist must be a pair */
+      SCM_ASSERT_TYPE (scm_is_pair (elem), alist, SCM_ARG1, FUNC_NAME,
+                       "association list");
+
+      c = scm_cons (scm_cons (SCM_CAR (elem), SCM_CDR (elem)), SCM_EOL);
+      *p = c;
+      p = SCM_CDRLOC (c);
+    }
+
+  /* alist must be a proper list */
+  SCM_ASSERT_TYPE (SCM_NULL_OR_NIL_P (alist), alist, SCM_ARG1, FUNC_NAME,
+                   "association list");
+  return ret;
+}
+#undef FUNC_NAME
+
+
 /* scm_append and scm_append_x don't modify their list argument (only the
    lists within that list in the case of scm_append_x), hence making them
    suitable for direct use for concatentate.  */

srfi/srfi-1.h

@@ -32,6 +32,7 @@
 # define SCM_SRFI1_API extern
 #endif
 
+SCM_SRFI1_API SCM scm_srfi1_alist_copy (SCM alist);
 SCM_SRFI1_API SCM scm_srfi1_count (SCM pred, SCM list1, SCM rest);
 SCM_SRFI1_API SCM scm_srfi1_delete (SCM x, SCM lst, SCM pred);
 SCM_SRFI1_API SCM scm_srfi1_delete_x (SCM x, SCM lst, SCM pred);

srfi/srfi-1.scm

@@ -618,13 +618,6 @@
 
 (define alist-cons acons)
 
-(define (alist-copy alist)
-  (let lp ((a alist)
-	   (rl '()))
-    (if (null? a)
-      (reverse! rl)
-      (lp (cdr a) (acons (caar a) (cdar a) rl)))))
-
 (define (alist-delete key alist . rest)
   (let ((k= (if (pair? rest) (car rest) equal?)))
     (let lp ((a alist) (rl '()))