Geometric types in SELECT?

  First off, thanks for the answer to my earlier question -- I've
become less misguided since (I hope!)
  One of my tables uses the point data type.  I wanted to use this to
find points close to one another.  Unfortunately, when I do something
like:

=>select * from address order by length ( '((0,0), coord)'::lseg );

or

=>select length( '((0,0),coord)'::lseg ) from address;

I receive this error:

Bad lseg external representation '((0,0), coord)'

If I replace coord with an actual value, I don't get the error. Am I
somehow mangling the syntax?  I've tried a number of different formats
for the query, with the same error each time.  Is it possible to do this?

Thanks,

-mike

-- 

And though the holes were rather small
They had to count them all
Now they know how many holes it takes to fill the Albert Hall
*I'd love to turn you on*
 -- Beatles, "A Day in the Life"

GnuPG key available at http://devel.duluoz.net/pubkey.asc
Key ID = 1024D/9A256AE5 1999-11-13 Mike Glover <mpg4@duluoz.net>
Key fingerprint = EF6E 8BCB 4810 E98C F0FD  4596 367A 32B7 9A25 6AE5