powerset?

[Ben <bench@xxxxxxxxxxxxxxx>]

Does anybody have a stored proc they'd like to share (preferably pl/ 
pgsql) that generates the power set of an array? For instance:

select powerset({1,2,3});

....would give 8 rows:

{}
{1}
{2}
{3}
{1,2}
{2,3}
{1,3}
{1,2,3}