functions/operators with 2 sets as arguments

While trying to create an operator to test if 2 intervals
overlap, I ran into the following limitation:

ERROR:  Functions and operators can take only one set argument
(PostgreSQL 7.3.2 on OpenBSD)

Does anybody know any workarounds (or if this limitation has been
removed from 7.4)?

Jochem

--
When you don't want to be surprised by the revolution
organize one yourself
     - Loesje