[postgis-users] POLYGON from LINESTRING

[Paul Ramsey]

Bernhard Reiter wrote:
> 
> On Wed, Apr 24, 2002 at 03:46:04PM -0700, Paul Ramsey wrote:
> > No there is not a simple way. Type casting is not specified in SFSQL.
> 
> Could have been a PostGIS addition or a commonly asked question,
> couldn't it? :)

Could be, and could still be. My main concern is that if we do something
like that now, we open the door to creating incredibly invalid
geometries. Ends touching is only one of the many criteria for a valid
polygon, and until we have our topology library we cannot test for all
the others. Imagine casting a figure 8 into a polygon. Ends touch, but
it is definately invalid.