simple Oracle 11 stored function

gistfile1.txt

CREATE OR REPLACE FUNCTION weekStartingFriday(dayval IN DATE)
RETURN DATE IS
adjustment NUMBER;
BEGIN
  adjustment := TO_NUMBER(TO_CHAR(dayval, 'D'));
  IF (adjustment >= 6) THEN
    adjustment := adjustment - 6;
  ELSE
    adjustment := adjustment + 1;
  END IF;
  RETURN(dayval - adjustment);
END;