selecting from $1

hi,
  using plpgsql im trying to do a select using $1 as the variable, this is
the query:

CREATE FUNCTION find_user (text) RETURNS text AS '
DECLARE
 ip text;
BEGIN
        select smtpip into ip from user_services where domain=$1;
        IF NOT FOUND THEN
           RAISE EXCEPTION ''Cant Find smtpip address for %'',$1;
           return;
        END IF;
        return ip;
END;
' LANGUAGE 'plpgsql';

i get the following error:

ERROR:  There is no operator '=$' for types 'varchar' and 'int4'
    You will either have to retype this query using an explicit cast,
    or you will have to define the operator using CREATE OPERATOR


if i change the =$1 to a 'like' then it works fine..help!

Paul
----------------------------------------------
Paul Kelly        pkelly@virtual.org.uk
U-NET Internet Noc    Some day now!