--- loncom/homework/radiobuttonresponse.pm	2003/05/16 19:25:08	1.71
+++ loncom/homework/radiobuttonresponse.pm	2003/06/20 04:05:13	1.72
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # mutliple choice style responses
 #
-# $Id: radiobuttonresponse.pm,v 1.71 2003/05/16 19:25:08 albertel Exp $
+# $Id: radiobuttonresponse.pm,v 1.72 2003/06/20 04:05:13 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -291,6 +291,8 @@ sub whichfoils {
 	}
     }
     #pick a true statement
+    my $notrue=0;
+    if (scalar(@truelist) == 0) { $notrue=1; }
     my $whichtrue = int(&Math::Random::random_uniform() * ($#truelist+1));
     &Apache::lonxml::debug("Max is $max, From $#truelist elms, picking $whichtrue");
     my (@toplist, @bottomlist);
@@ -319,8 +321,12 @@ sub whichfoils {
     &Apache::lonxml::debug("Answer wants $answer");
     my $truename=$truelist[$whichtrue];
     my $dosplice=1;
+    if ($notrue) {
+	$dosplice=0;
+	&Apache::lonxml::error("There are no true statements available.<br />");
+    }
     #insert the true statement, keeping track of where it wants to be
-    if ($Apache::response::foilgroup{$truename.'.location'} eq 'top' ) {
+    if ($Apache::response::foilgroup{$truename.'.location'} eq 'top' && $dosplice) {
 	$toplist[$top{$truename}]=$truename;
 	$answer=-1;
 	foreach my $top (reverse(@toplist)) {
@@ -328,7 +334,7 @@ sub whichfoils {
 	    if ($top eq $truename) { last; }
 	}
 	$dosplice=0;
-    } elsif ($Apache::response::foilgroup{$truename.'.location'} eq 'bottom') {
+    } elsif ($Apache::response::foilgroup{$truename.'.location'} eq 'bottom' && $dosplice) {
 	$bottomlist[$bottom{$truename}]=$truename;
 	$answer=-1;
 	foreach my $bot (@bottomlist) {