1452     def visit_mathexpression(self, mexpr):

  1452     def visit_mathexpression(self, mexpr):

  1453         """generate SQL for a mathematic expression"""

  1453         """generate SQL for a mathematic expression"""

  1454         lhs, rhs = mexpr.get_parts()

  1454         lhs, rhs = mexpr.get_parts()

  1455         # check for string concatenation

  1455         # check for string concatenation

  1456         operator = mexpr.operator

  1456         operator = mexpr.operator

  1457         try:

  1459         try:

  1458             if mexpr.operator == '+' and mexpr.get_type(self._state.solution, self._args) == 'String':

  1460             if mexpr.operator == '+' and mexpr.get_type(self._state.solution, self._args) == 'String':

  1459                 return '(%s)' % self.dbhelper.sql_concat_string(lhs.accept(self),

  1461                 return '(%s)' % self.dbhelper.sql_concat_string(lhs.accept(self),

  1460                                                                 rhs.accept(self))

  1462                                                                 rhs.accept(self))

  1461         except CoercionError:

  1463         except CoercionError: