create function(date,date,date,...)

Hi,

i am trying to declare function that gets six date arguments
and returns some status according actual date. It looks like
this:

CREATE FUNCTION datum_ok(DATE,DATE,DATE,DATE,DATE,DATE) RETURNS TEXT AS '
DECLARE tests         ALIAS FOR $1 ; teste         ALIAS FOR $2 ; payments      ALIAS FOR $3 ; paymente      ALIAS FOR
$4; interrupts    ALIAS FOR $5 ; interrupte    ALIAS FOR $6 ; today         DATE ;
 
BEGIN today := now()::date ; .....

It happens that when some argument is NULL, than all argument get NULL.
It works correctly only when all arguments are not NULL.

SELECT  login,  datum_ok(    test_start, test_end,    payment_start, payment_end,    interrupt_start, interrupt_end )
FROM service ;

How can I mix NULL and DATE values in arguments?

Thanks

Radek Kanovsky, rk@uh.cz