PL/pgsql declaration of string / bit / number with given (variable!) length

Hi,

I have a PL/pgsql function that creates a certain bit string
based on the parameters. Things work fine if I use bit(10)
throughout the function. Now I'd like to return a bit string
with the given size "len", but that breaks with a syntax error:

ret := B'0'::bit(len);
LINE 1: SELECT B'0'::bit( $1 )
^

Any suggestion how to return a (bit) string
of user-defined length ?

Thanks in advance,
Yours,
Steffen

CREATE OR REPLACE FUNCTION unarystr(
value integer,
len integer
) RETURNS bit(10) AS $$
DECLARE
ret bit(10);
one bit(10);
BEGIN
ret := B'0'::bit(10);
one := B'1'::bit(10);

FOR num IN 0..value-1 LOOP
ret := ret | (one >>num);
END LOOP;
RETURN ret;
END;
$$ LANGUAGE plpgsql;

--
IPB Halle AG Massenspektrometrie & Bioinformatik
Dr. Steffen Neumann http://www.IPB-Halle.DE
Weinberg 3 http://msbi.bic-gh.de
06120 Halle New phone number !
Tel. +49 (0) 345 5582 - 1470
+49 (0) 345 5582 - 0
sneumann(at)IPB-Halle.DE Fax. +49 (0) 345 5582 - 1409