OUT/IN OUT parameters in PL/SQL function

Question

as far as I understood it, it is only possible to have OUT or IN OUT parameters for procedures, not functions. However, when defining a user-defined aggregate function, I have found this signature:

member FUNCTION ODCIAggregateIterate(self IN OUT DeviationImpl,
value IN NUMBER) RETURN NUMBER

This seems to be a function, however, it has an IN OUT parameter. Could somebody explain me why is this possible?

Thanks

Solution

There is no such restrictions. Functions can have OUT or IN OUT parameters.

However, Oracle recommends against using them.

OUT and IN OUT parameters prevent a function from being used from plain SQL, marked as a DETERMINISTIC function or used as a result-cached function. So these type of parameters are mainly a problem if you want to use the function in a SQL query.

Your example is even more specific: it's a member function, not a global function.