The unary operator ! turns the
path of sline objects, but preserves
begin and end of the spherical line. The length of
returned line will be 360° minus the line length
of operator's argument.
The operator ! returns
NULL, if the length of sline argument
is 0, because the path of returned sline
is undefined.
Example 5.15. Return length and check if north pole on slines
sql> SELECT set_sphere_output('DEG');
set_sphere_output
-------------------
SET DEG
(1 row)
sql> SELECT length ( sline ( spoint '(0d,0d)', spoint '(0d,10d)' ) ) *
180.0 / pi() AS length;
length
--------
10
(1 row)
sql> SELECT spoint '(0d,90d)' @
sline ( spoint '(0d,0d)', spoint '(0d,10d)' ) AS test;
test
------
f
(1 row)
sql> SELECT length ( ! sline ( spoint '(0d,0d)', spoint '(0d,10d)' ) ) *
180.0 / pi() AS length;
length
--------
350
(1 row)
sql> SELECT spoint '(0d,90d)' @
! sline ( spoint '(0d,0d)', spoint '(0d,10d)' ) AS test;
test
------
t
(1 row)