Oracle generic datatype that can be cast as other datatype ?

Question

I have a function that currently returns a DATE datatype but want to provide functionality so that depending on the value of a parameter it will return either a DATE or a VARCHAR2. For example
FUNCTION AddDate(p_dt_DateIn IN DATE, p_vch_DType IN VARCHAR2)
RETURN ????? IS
IF UPPER(p_vch_DType) = 'C' THEN
RETURN TO_CHAR(p_dt_DateIn + 2, 'DD Mon YYYY')
ELSE
RETURN p_dt_DateIn + 2
END IF;
The calling procedure would then cast the returned type.
Does a generic datatype like this exist in Oracle ? I've been looking at overloading using packages but it basically boils down to using two seperate functions for each returned datatype which i really don't want to do.

Answer 1

Normally, we would implement this as overloaded functions in a package:
CREATE PACKAGE my_package AS
  FUNCTION addDate (p_dt_DateIn IN DATE) RETURN DATE;
  FUNCTION addDate (p_vc_DateIn IN VARCHAR2) RETURN VARCHAR2;
END;the point being that in the package body the varchar version can call the date version, so you actually only code the process once.
The advantage of this approach is that the calling program doesn't have to cast the result, because Oracle uses the right function for the parameter data type.
Cheers, APC