Functions Deterministic 
<parameters> [IN | OUT | IN OUT] [NOCOPY] <data_type>)
DETERMINISTIC
RETURN <data_type> [AUTHID <CURRENT_USER | DEFINER>] IS
 
<constant, EXCEPTION, AND variable declarations>
 
BEGIN
  <code_here>;
END <function_name>;
/ 
CREATE OR REPLACE PACKAGE fd_demo IS
 td DATE;
 
 FUNCTION get_date RETURN DATE;
 FUNCTION get_date_determ RETURN DATE DETERMINISTIC;
END fd_demo;
/
 
CREATE OR REPLACE PACKAGE BODY df_demo IS
 
 FUNCTION get_date RETURN DATE IS
 BEGIN
   RETURN df_demo.td;
 END get_date;
 
 FUNCTION get_date_determ RETURN DATE DETERMINISTIC IS
 BEGIN
   RETURN df_demo.td;
 END get_date_determ;
 
END df_demo;
/