point(lseg,lseg) does not exist

Hi,

I am attempting a query using lseg values to find the point
of intersection. The following query taken from the PG
manual isn't working over here.

select
point(lseg '((-1,0),(1,0))', lseg
'((-2,-2),(2,2))')
ERROR: function point(lseg, lseg) does not exist
HINT: No function matches the given name and argument
types. You may need to add explicit type casts.

Do I need to declare this function somewhere? Pg version
7.4.7 (debian rev 6 Sarge).

Best regards,
Shane

--
Shane Wegner
http://www.cm.nu/~shane/