private void addComplexExpression(DRIDesignComplexExpression complexExpression) {
   if (complexExpressions.containsKey(complexExpression.getName())) {
     if (!complexExpressions.get(complexExpression.getName()).equals(complexExpression)) {
       throw new DRDesignReportException(
           "Duplicate declaration of complex expression \"" + complexExpression.getName() + "\"");
     }
     return;
   }
   complexExpressions.put(complexExpression.getName(), complexExpression);
 }