postgres lat/lon projection functions

gistfile1.txt

CREATE OR REPLACE FUNCTION worldSize (maxZoom int, tileSize int)
RETURNS int AS $$
  DECLARE
    size int;
  BEGIN
    size := power(2, maxZoom) * tileSize;
    RETURN size;
  END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION xLng (x int, worldSize int)
RETURNS double precision AS $$
  DECLARE
    lng double precision;
  BEGIN
    lng := ((x * 360)::float / worldSize::float) - 180;
    RETURN lng;
  END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION yLat (y int, worldSize int)
RETURNS double precision AS $$
  DECLARE
    y2 double precision;
    lat double precision;
  BEGIN
    y2  := 180::float - y * 360::float / worldSize::float;
    lat := 360::float / pi() * atan(exp(y2 * pi() / 180::float)) - 90;
    RETURN lat;
  END;
$$ LANGUAGE plpgsql;