using functions defined in the sql with clause?

another nice features of oracle 12cR1: you may define functions within the sql with clause:

SQL> !cat a.sql
WITH
  FUNCTION f_test ( a NUMBER) RETURN NUMBER
  IS
  BEGIN
    return a * 2;
  END;
select f_test (5) from dual;
/

SQL> @a

 F_TEST(5)
----------
	10

this is particulary useful when you are not allowed to created stored procedures or you are connected to a read only database.