anchor.diff:  import com.metamx.druid.query.filter.*;
   import com.metamx.druid.query.dimension.*;
   import com.metamx.druid.*;
  +
   import com.google.common.base.*;
   import com.google.common.collect.Lists;
  +import org.joda.time.*;
  +
  +import java.text.*;
   import java.util.*;
  -import org.joda.time.*;
   }
   
   @parser::members {
  
positive.code:     }
      ;
  
  timestamp
      : DOUBLE | QUOTED_STRING
      ;
  
negative.code:         $p = new ArithmeticPostAggregator(
              "-"+$e.p.getName(),
              "*",
              Lists.newArrayList($e.p, new ConstantPostAggregator("-1", -1.0))
          );
      }
      | PLUS e=unaryExpression { $p = $e.p; }
  