--- loncom/homework/radiobuttonresponse.pm	2003/04/18 17:10:08	1.70
+++ 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 1.70 2003/04/18 17:10:08 sakharuk Exp $
+# $Id: radiobuttonresponse.pm,v 1.72 2003/06/20 04:05:13 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -291,13 +291,16 @@ 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);
     my $topcount=0;
+    my $bottomcount=0;
     # assign everyone to either toplist/bottomlist or whichfalse
     # which false is randomized, toplist bottomlist are in order
-    while ((($#whichfalse) < $max-2) && ($#falselist > -1)) {
+    while ((($#whichfalse+$topcount+$bottomcount) < $max-2) && ($#falselist > -1)) {
 	&Apache::lonxml::debug("Have $#whichfalse max is $max");
 	my $afalse=int(&Math::Random::random_uniform() * ($#falselist+1));
 	&Apache::lonxml::debug("From $#falselist elms, picking $afalse");
@@ -310,14 +313,20 @@ sub whichfoils {
 	    $topcount++;
 	} elsif ($bottom{$afalse}) {
 	    $bottomlist[$bottom{$afalse}]=$afalse;
+	    $bottomcount++;
 	} else {
 	    push (@whichfalse,$afalse);
 	}
     }
+    &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 $top (reverse(@toplist)) {
@@ -325,7 +334,7 @@ sub whichfoils {
 	    if ($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) {
@@ -335,11 +344,12 @@ sub whichfoils {
 	$answer+=$topcount+$#whichfalse+1;
 	$dosplice=0;
     } else {
-	if ($topcount>0) { 
-	  $answer = int(&Math::Random::random_uniform() * ($#whichfalse+1))
-	    + $topcount;
+	if ($topcount>0 || $bottomcount>0) {
+	    $answer = int(&Math::Random::random_uniform() * ($#whichfalse+1))
+		+ $topcount;
 	}
     }
+    &Apache::lonxml::debug("Answer now wants $answer");
     #add the top items to the top, bottom items to the bottom
     for (my $i=0;$i<=$#toplist;$i++) {
 	if ($toplist[$i]) { unshift(@whichfalse,$toplist[$i]) }