What is ##?

geometry regression test:

QUERY: SELECT '' AS thirty, p.f1, l.s, p.f1 ## l.s AS closest
FROM LSEG_TBL l, POINT_TBL p;
thirty|f1 |s |closest

------+----------+-----------------------------+--------------------------------
----
|(0,0) |[(1,2),(3,4)] |(1,2)

|(-10,0) |[(1,2),(3,4)] |(1,2)

|(-3,4) |[(1,2),(3,4)] |(1,2)

|(5.1,34.5)|[(1,2),(3,4)] |(3,4)

|(-5,-12) |[(1,2),(3,4)] |(1,2)

|(10,10) |[(1,2),(3,4)] |(3,4)

|(0,0) |[(0,0),(6,6)] |(-0,0)

This last line, in the current results, provides a value of (0,0) for
closest, but I can't find what ## means in order to determine if this is
as expected...

Marc G. Fournier
Systems Administrator @ hub.org
primary: scrappy(at)hub(dot)org secondary: scrappy(at){freebsd|postgresql}.org