Determining if two subnets intersect

Is there some efficient PostgreSQL expression which is true if and
only if two subnets (given as values of type cidr) have non-empty
intersection (even if the intersection is not a CIDR network)?

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Florian Weimer                       Florian.Weimer@RUS.Uni-Stuttgart.DE
University of Stuttgart           http://cert.uni-stuttgart.de/
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