@Override
 public String prettyPrint(
     SQLSkin skin, OperatorPiece piece, OperatorDefinition opDef, String[] args)
     throws RenderingException {
   if (args.length == 1) {
     return prettyPrintSingleArg(skin, opDef, piece, args);
   } else if (args.length == 2) {
     return prettyPrintTwoArgs(skin, piece, opDef, args);
   } else {
     if (CastOperatorDefinition.TO_NUMBER.equals(opDef.getExtendedID())) {
       return prettyPrintSingleArg(skin, opDef, piece, args);
     } else {
       throw new RenderingException("Invalid operator " + opDef.getSymbol());
     }
   }
 }