help needs in converting db2 function in postgresql.

Hi,
I need helping converting following db2 function in postgresql function.
Any pointer will be great help in proceeding me ahead.

CREATE FUNCTION in_liststring ( string CLOB(64K) )   RETURNS TABLE ( ordinal INTEGER, index INTEGER )   LANGUAGE SQL
DETERMINISTIC  NO EXTERNAL ACTION   CONTAINS SQL   RETURN      WITH t(ordinal, index) AS         ( VALUES ( 0, 0 )
    UNION ALL           SELECT ordinal+1, COALESCE(NULLIF(                     -- find the next delimiter ','
         LOCATE(',', string, index+1), 0),                     LENGTH(string)+1)           FROM   t                  --
toprevent a warning condition for infinite                  -- recursions, we add the explicit upper
--boundary for the "ordinal" values           WHERE  ordinal < 10000 AND                  -- terminate if
thereare no further delimiters                  -- remaining                  LOCATE(',', string, index+1) <> 0 )
SELECTordinal, index      FROM   t      UNION ALL      -- add indicator for the end of the string      SELECT
MAX(ordinal)+1,LENGTH(string)+1      FROM   t 
;

commit;

DROP FUNCTION INSTRTBL;

CREATE FUNCTION INSTRTBL ( string CLOB(64K) )   RETURNS TABLE ( INSTRTBL CLOB(64K) )   LANGUAGE SQL   DETERMINISTIC
NOEXTERNAL ACTION   CONTAINS SQL   RETURN      WITH t(ordinal, index) AS         ( SELECT ordinal, index           FROM
 TABLE ( in_liststring(string) ) AS x )      SELECT SUBSTR(string, t1.index+1, t2.index - t1.index - 1)      -- the
joinbelow makes sure that we have the lower and      -- upper index where we can find each of the ',' delimiters
--that are separating the INSTRTBL.  (For this, we exploit      -- the additional indexes pointing to the beginning and
end     -- of the string.)      FROM   t AS t1 JOIN t AS t2 ON                ( t2.ordinal = t1.ordinal+1 ) 
;