--- loncom/interface/loncommon.pm	2009/05/16 18:06:41	1.819
+++ loncom/interface/loncommon.pm	2009/05/18 16:08:07	1.820
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.819 2009/05/16 18:06:41 tempelho Exp $
+# $Id: loncommon.pm,v 1.820 2009/05/18 16:08:07 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -10212,6 +10212,22 @@ sub escape_url {
     return join('/',@urlslices).'/'.$lastitem;
 }
 
+sub compare_arrays {
+    my ($arrayref1,$arrayref2) = @_;
+    my (@difference,%count);
+    @difference = ();
+    %count = ();
+    if ((ref($arrayref1) eq 'ARRAY') && (ref($arrayref2) eq 'ARRAY')) {
+        foreach my $element (@{$arrayref1}, @{$arrayref2}) { $count{$element}++; }
+        foreach my $element (keys(%count)) {
+            if ($count{$element} == 1) {
+                push(@difference,$element);
+            }
+        }
+    }
+    return @difference;
+}
+
 # -------------------------------------------------------- Initialize user login
 sub init_user_environment {
     my ($r, $username, $domain, $authhost, $form, $args) = @_;