--- loncom/homework/default_homework.lcpm	2008/09/13 02:08:32	1.140
+++ loncom/homework/default_homework.lcpm	2009/04/17 01:00:15	1.144
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA 
 # used by lonxml::xmlparse() as input variable $safeinit to Apache::run::run()
 #
-# $Id: default_homework.lcpm,v 1.140 2008/09/13 02:08:32 raeburn Exp $
+# $Id: default_homework.lcpm,v 1.144 2009/04/17 01:00:15 www Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -217,7 +217,13 @@ sub caparesponse_check {
 
     my $reterror="";
     my $result;
-    if ((($type eq '9') || ($type eq '8')) && ($response=~/\=/)) { return ('BAD_FORMULA','Please submit just an expression, not an equation.'); }
+    if (($type eq '9') || ($type eq '8')) {
+        if ($response=~/\=/) {
+            return ('BAD_FORMULA','Please submit just an expression, not an equation.');
+        } elsif ($response =~ /\,/ and $response !~ /^\s*\{.*\}\s*$/) {
+            return ('BAD_FORMULA');
+        }
+    }
     if ($type eq '9') {
       $result = &maxima_check(&maxima_cas_formula_fix($response),&maxima_cas_formula_fix($answer),\$reterror);
     } else {
@@ -320,7 +326,7 @@ sub caparesponse_check_list {
               $element =~ s/\s//g;
           }
           my $appendunit=$unit;
-          if ($unit=~/\%/) {
+          if (($unit=~/\%/) && ($answerunit ne '%'))  {
              $element=$element/100;
              $appendunit=~s/\%//;
           }    
@@ -430,6 +436,8 @@ sub cas {
     my $output;
     if ($system eq 'maxima') {
        $output=&maxima_eval($input,$library);
+    } elsif ($system eq 'R') {
+       $output=&r_eval($input,$library);
     } else {
        $output='Error: unrecognized CAS';
     }