code: func Area(db XODB, v0 pgtypes.Path, v1 pgtypes.Box, v2 pgtypes.Circle) (float64, error) {
  	var err error
  
  	// sql query
  	const sqlstr = `SELECT pg_catalog.area($1, $2, $3)`
  
  	// run query
  	var ret float64
  	XOLog(sqlstr, v0, v1, v2)
  	err = db.QueryRow(sqlstr, v0, v1, v2).Scan(&ret)
  	if err != nil {
  		return 0.0, err
  	}
  
  	return ret, nil
  }
docs: // Area calls the stored procedure 'pg_catalog.area(path, box, circle) double precision' on db.