[WWcvs] pg: Added ability to specify variables that are part of the union/list

[dpvc v. a. <we...@ma...>]

Log Message:
-----------
Added ability to specify variables that are part of the union/list
rather than requiring just constants.  E.g.,

       interval_cmp("(1,a),(2a-1,a)",unions=>'no',var=>'a');

or 

       interval_cmp("(x,y),(2x,3y)",unions=>'no',vars=>['x','y']);

Modified Files:
--------------
    pg/macros:
        extraAnswerEvaluators.pl

Revision Data
-------------
Index: extraAnswerEvaluators.pl
===================================================================
RCS file: /webwork/cvs/system/pg/macros/extraAnswerEvaluators.pl,v
retrieving revision 1.13
retrieving revision 1.14
diff -Lmacros/extraAnswerEvaluators.pl -Lmacros/extraAnswerEvaluators.pl -u -r1.13 -r1.14
--- macros/extraAnswerEvaluators.pl
+++ macros/extraAnswerEvaluators.pl
@@ -344,6 +344,17 @@
 			$ans_type = 'String' if $string eq uc($correct_ans);
 		}
 	}
+	# Add any variables
+	$opts{vars} = $opts{var} if ($opts{var});
+	if ($opts{vars}) {
+		$context->variables->are(); # clear old vars
+		$opts{vars} = [$opts{vars}] unless ref($opts{vars}) eq 'ARRAY';
+		foreach my $v (@{$opts{vars}}) {
+			$context->variables->add($v=>'Real')
+				unless $context->variables->get($v);
+		}
+	}
+	
 	my $ans_eval;
 	Context($context);
 	if($ans_type eq 'List') {