How to join function with a table?

Hi everyone,
I have a function returning set of date called datelist(date,date)
example:
select * from datelist('8/1/2005, 8/5/2005');
8/1/2005
8/2/3005
8/3/2004
8/4/2005
8/5/2005
I would like to join this function with a table
create table payment(
id int4 not null,
date_start date,
date_end date
)
id | date_start | date_end
----------------------------------------
1 | 8/1/2005 | 8/2/2005
2 | 8/4/2005 | 8/6/2005
I wish I could do join that returns something like this with the function
id | datelist
------------------
1 | 8/1/2005
1 | 8/2/2005
2 | 8/4/2005
2 | 8/5/2005
2 | 8/6/2005
I thought simple join like this would work, but it doesn't
select * from payment P, datelist(P.date_start, P.date_end)
because it require a relation.
help is appreciated.
Yudie