SCOTT@orcl_12.1.0.2.0> CREATE OR REPLACE FUNCTION couponcd
  2    (p_settlement IN DATE,
  3  	p_maturity   IN DATE,
  4  	p_frequency  IN INTEGER)
  5    RETURN DATE
  6  AS
  7  BEGIN
  8    -- check for input errors:
  9    IF p_frequency NOT IN (1, 2, 4) THEN
 10  	 RAISE_APPLICATION_ERROR (-20001, 'Frequency must be 1 or 2 or 4!');
 11    END IF;
 12    IF TRUNC (p_settlement) >= TRUNC (p_maturity) THEN
 13  	 RAISE_APPLICATION_ERROR (-20002, 'Settlement cannot be >= maturity!');
 14    END IF;
 15    -- calculate and return next coupon date:
 16    RETURN ADD_MONTHS
 17  		(TRUNC (p_maturity),
 18  		 ((12 / p_frequency) * TRUNC (MONTHS_BETWEEN (p_settlement, p_maturity) / (12 / p_frequency))));
 19  END couponcd;
 20  /

Function created.

SCOTT@orcl_12.1.0.2.0> SHOW ERRORS
No errors.
SCOTT@orcl_12.1.0.2.0> SELECT couponcd
  2  	      (TO_DATE ('01-01-2011', 'DD-MM-YYYY'),
  3  	       TO_DATE ('15-11-2011', 'DD-MM-YYYY'),
  4  	       2)
  5  FROM   DUAL
  6  /

COUPONCD(TO
-----------
15-MAY-2011

1 row selected.