calling user defined function with parameters..

Hi,

I've created a function like this :

CREATE FUNCTION tester(INT4)
RETURNS BOOL AS
'
DECLARE
r RECORD;
p ALIAS FOR $1;

BEGIN
SELECT INTO r
id_dpt
FROM dpts
WHERE id_dpt=p;

IF NOT FOUND THEN
RETURN FALSE;
ELSE

RETURN TRUE;
END IF;
END;
'
LANGUAGE 'plpgsql';

All is ok at creation.
But now , how can i use my function ? i would like a thing like :

SELECT tester(14) AS ok;

But is make a Postgresql parser error

How to do then ??

Thanks for any help or links (other than the postgresql.org website...) !

;)

Regards,

Fred