text: /* contrib/earthdistance/earthdistance--1.0.sql */
  
  -- complain if script is sourced in psql, rather than via CREATE EXTENSION
  \echo Use "CREATE EXTENSION earthdistance" to load this file. \quit
  
  -- earth() returns the radius of the earth in meters. This is the only
  -- place you need to change things for the cube base distance functions
  -- in order to use different units (or a better value for the Earth's radius).
  
  CREATE FUNCTION earth() RETURNS float8
  LANGUAGE SQL IMMUTABLE
  AS 'SELECT ''6378168''::float8';
  
  -- Astromers may want to change the earth function so that distances will be
  -- returned in degrees. To do this comment out the above definition and
  -- uncomment the one below. Note that doing this will break the regression
  -- tests.
  --
  -- CREATE FUNCTION earth() RETURNS float8
  -- LANGUAGE SQL IMMUTABLE
  -- AS 'SELECT 180/pi()';
  
  -- Define domain for locations on the surface of the earth using a cube
  -- datatype with constraints. cube provides 3D indexing.
  -- The cube is restricted to be a point, no more than 3 dimensions
  -- (for less than 3 dimensions 0 is assumed for the missing coordinates)
  -- and that the point must be very near the surface of the sphere
  -- centered about the origin with the radius of the earth.
  
  CREATE DOMAIN earth AS cube
    CONSTRAINT not_point check(cube_is_point(value))
    CONSTRAINT not_3d check(cube_dim(value) <= 3)
    CONSTRAINT on_surface check(abs(cube_distance(value, '(0)'::cube) /
    earth() - 1) < '10e-7'::float8);
  
  CREATE FUNCTION sec_to_gc(float8)
  RETURNS float8
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT CASE WHEN $1 < 0 THEN 0::float8 WHEN $1/(2*earth()) > 1 THEN pi()*earth() ELSE 2*earth()*asin($1/(2*earth())) END';
  
  CREATE FUNCTION gc_to_sec(float8)
  RETURNS float8
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT CASE WHEN $1 < 0 THEN 0::float8 WHEN $1/earth() > pi() THEN 2*earth() ELSE 2*earth()*sin($1/(2*earth())) END';
  
  CREATE FUNCTION ll_to_earth(float8, float8)
  RETURNS earth
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT cube(cube(cube(earth()*cos(radians($1))*cos(radians($2))),earth()*cos(radians($1))*sin(radians($2))),earth()*sin(radians($1)))::earth';
  
  CREATE FUNCTION latitude(earth)
  RETURNS float8
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT CASE WHEN cube_ll_coord($1, 3)/earth() < -1 THEN -90::float8 WHEN cube_ll_coord($1, 3)/earth() > 1 THEN 90::float8 ELSE degrees(asin(cube_ll_coord($1, 3)/earth())) END';
  
  CREATE FUNCTION longitude(earth)
  RETURNS float8
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT degrees(atan2(cube_ll_coord($1, 2), cube_ll_coord($1, 1)))';
  
  CREATE FUNCTION earth_distance(earth, earth)
  RETURNS float8
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT sec_to_gc(cube_distance($1, $2))';
  
  CREATE FUNCTION earth_box(earth, float8)
  RETURNS cube
  LANGUAGE SQL
  IMMUTABLE STRICT
  AS 'SELECT cube_enlarge($1, gc_to_sec($2), 3)';
  
  --------------- geo_distance
  
  CREATE FUNCTION geo_distance (point, point)
  RETURNS float8
  LANGUAGE C IMMUTABLE STRICT AS 'MODULE_PATHNAME';
  
  --------------- geo_distance as operator <@>
  
  CREATE OPERATOR <@> (
    LEFTARG = point,
    RIGHTARG = point,
    PROCEDURE = geo_distance,
    COMMUTATOR = <@>
  );
  