invoking methods on php's stdClass

I figured out a way to add methods and call them on the stdClass object, using anonymous functions:

$obj = new stdClass();
$anon = function ($value) { return "My value is $value." ; } ;

$obj->value = "a";
$obj->method = $anon;

$method = $obj->method;
echo $method($obj->value) . "\n";

Migrating an Adjacency List

Adjacency lists and modified preorder trees are two ways of storing nested hierarchies in a relational database. For some good background on these structures, see here.

So the adjacency list is probably one that's intuitive and easy to come up with if you are to to the field. However, once you learn the benefits of the preorder tree, you'll probably want to migrate. But the migration is not so easy as a few queries -- you'll need an algorithm to do so, and a recursive one at that.

Here's a couple stored procedures for MySQL that will migrate data from an adjacency list to a modified preorder traversal tree:


First I'll set up an adjacency list (language family data from wikipedia):

 CREATE TABLE IF NOT EXISTS `language_family_adj_list` (
    `language_id` int(11) NOT NULL auto_increment,
    `language` varchar(20) NOT NULL,
    `parent_id` int(11) default NULL,
    PRIMARY KEY  (`language_id`)
  ) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=41 ;


  INSERT INTO `language_family_adj_list` (`language_id`, `language`, `parent_id`) VALUES
  (1, 'Finno-Ugric', NULL),
  (2, 'Hungarian', 1),
  (3, 'Khanty', 1),
  (4, 'Mansi', 1),
  (5, 'Permic', 1),
  (6, 'Mari', 1),
  (7, 'Mordvinic', 1),
  (8, 'Sami', 1),
  (9, 'Baltic-Finnic', 1),
  (10, 'Komi', 5),
  (11, 'Komi-Permyak', 5),
  (12, 'Udmurt', 5),
  (13, 'Erzya', 7),
  (14, 'Moksha', 7),
  (15, 'Western Sami', 8),
  (16, 'Eastern Sami', 8),
  (17, 'Southern Sami', 15),
  (18, 'Umi Sami', 15),
  (19, 'Lule Sami', 15),
  (20, 'Pite Sami', 15),
  (22, 'Northern Sami', 15),
  (23, 'Kemi Sami', 16),
  (24, 'Inari Sami', 16),
  (25, 'Akkala Sami', 16),
  (26, 'Kildin Sami', 16),
  (27, 'Skolt Sami', 16),
  (28, 'Ter Sami', 16),
  (29, 'Estonian', 9),
  (30, 'Finnish', 9),
  (31, 'Ingrian', 9),
  (32, 'Karelian', 9),
  (33, 'Livonian', 9),
  (34, 'Veps', 9),
  (35, 'Votic', 9),
  (36, 'South Estonian', 29),
  (37, 'Voro', 36),
  (38, 'Karelian Proper', 32),
  (39, 'Lude', 32),
  (40, 'Olonets Karelian', 32);

Here's a query to demonstrate:

  mysql> SELECT t1.language AS lev1, t2.language as lev2, t3.language as lev3, t4.language as lev4, t5.language AS lev5
      -> FROM language_family_adj_list AS t1
      -> LEFT JOIN language_family_adj_list AS t2 ON t2.parent_id = t1.language_id
      -> LEFT JOIN language_family_adj_list AS t3 ON t3.parent_id = t2.language_id
      -> LEFT JOIN language_family_adj_list AS t4 ON t4.parent_id = t3.language_id
      -> LEFT JOIN language_family_adj_list AS t5 ON t5.parent_id = t4.language_id
      -> WHERE t1.parent_id IS NULL
      -> ORDER BY t1.language, t2.language, t3.language, t4.language, t5.language;
  +-------------+---------------+--------------+------------------+------+
  | lev1        | lev2          | lev3         | lev4             | lev5 |
  +-------------+---------------+--------------+------------------+------+
  | Finno-Ugric | Baltic-Finnic | Estonian     | South Estonian   | Voro |
  | Finno-Ugric | Baltic-Finnic | Finnish      | NULL             | NULL |
  | Finno-Ugric | Baltic-Finnic | Ingrian      | NULL             | NULL |
  | Finno-Ugric | Baltic-Finnic | Karelian     | Karelian Proper  | NULL |
  | Finno-Ugric | Baltic-Finnic | Karelian     | Lude             | NULL |
  | Finno-Ugric | Baltic-Finnic | Karelian     | Olonets Karelian | NULL |
  | Finno-Ugric | Baltic-Finnic | Livonian     | NULL             | NULL |
  | Finno-Ugric | Baltic-Finnic | Veps         | NULL             | NULL |
  | Finno-Ugric | Baltic-Finnic | Votic        | NULL             | NULL |
  | Finno-Ugric | Hungarian     | NULL         | NULL             | NULL |
  | Finno-Ugric | Khanty        | NULL         | NULL             | NULL |
  | Finno-Ugric | Mansi         | NULL         | NULL             | NULL |
  | Finno-Ugric | Mari          | NULL         | NULL             | NULL |
  | Finno-Ugric | Mordvinic     | Erzya        | NULL             | NULL |
  | Finno-Ugric | Mordvinic     | Moksha       | NULL             | NULL |
  | Finno-Ugric | Permic        | Komi         | NULL             | NULL |
  | Finno-Ugric | Permic        | Komi-Permyak | NULL             | NULL |
  | Finno-Ugric | Permic        | Udmurt       | NULL             | NULL |
  | Finno-Ugric | Sami          | Eastern Sami | Akkala Sami      | NULL |
  | Finno-Ugric | Sami          | Eastern Sami | Inari Sami       | NULL |
  | Finno-Ugric | Sami          | Eastern Sami | Kemi Sami        | NULL |
  | Finno-Ugric | Sami          | Eastern Sami | Kildin Sami      | NULL |
  | Finno-Ugric | Sami          | Eastern Sami | Skolt Sami       | NULL |
  | Finno-Ugric | Sami          | Eastern Sami | Ter Sami         | NULL |
  | Finno-Ugric | Sami          | Western Sami | Lule Sami        | NULL |
  | Finno-Ugric | Sami          | Western Sami | Northern Sami    | NULL |
  | Finno-Ugric | Sami          | Western Sami | Pite Sami        | NULL |
  | Finno-Ugric | Sami          | Western Sami | Southern Sami    | NULL |
  | Finno-Ugric | Sami          | Western Sami | Umi Sami         | NULL |
  +-------------+---------------+--------------+------------------+------+
  29 rows in set (0.00 sec)

So here's the modified preorder traversal tree table schema:

  CREATE TABLE language_family_mptt (
   language VARCHAR(30) NOT NULL,
   lft INT NOT NULL,
   rgt INT NOT NULL
  ) COLLATE utf8;

And then here's the recursive stored procedure to migrate the data:

  TRUNCATE TABLE language_family_mptt;
  SET max_sp_recursion_depth = 255;
  DROP PROCEDURE IF EXISTS insert_branches;
  DROP PROCEDURE IF EXISTS start_tree;
  DELIMITER ~~

  CREATE PROCEDURE start_tree()
  BEGIN
      DECLARE language_field VARCHAR(100);
      DECLARE done INT DEFAULT 0;
      DECLARE insert_id INT;
      DECLARE source_id INT;
   
      DECLARE cursor1 CURSOR FOR SELECT language, language_id FROM language_family_adj_list WHERE parent_id IS NULL ORDER BY language;
   
      DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
   
      OPEN cursor1;
      read_loop: LOOP
       
          SET @my_left = 1;
       
          FETCH cursor1 INTO language_field, source_id;
          INSERT INTO language_family_mptt ( language, lft ) VALUES ( language_field, 1 );
               
          CALL insert_branches( source_id );
       
          UPDATE language_family_mptt SET rgt = @my_left + 1 WHERE lft = 1 AND rgt = 0;
       
          IF done THEN
              LEAVE read_loop;
          END IF;
               
      END LOOP;
      CLOSE cursor1;

  END; ~~

  CREATE PROCEDURE insert_branches( IN source_parent_id INT )
  BEGIN
      DECLARE done INT DEFAULT 0;
      DECLARE next_source_parent_id INT DEFAULT NULL;
      DECLARE orig_left INT DEFAULT NULL;
      DECLARE language_field VARCHAR(100); 
      DECLARE cursor1 CURSOR FOR SELECT language_id, language FROM language_family_adj_list WHERE parent_id = source_parent_id ORDER BY language;
      DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
   
      OPEN cursor1;
   
      read_loop: LOOP
               
          FETCH cursor1 INTO next_source_parent_id, language_field;
       
          IF done THEN
              LEAVE read_loop;
          END IF;
        
          SET @my_left = @my_left + 1;
       
          INSERT INTO language_family_mptt ( language, lft ) VALUES ( language_field, @my_left );
       
          SET orig_left = @my_left;
       
          CALL insert_branches( next_source_parent_id );
       
          UPDATE language_family_mptt SET rgt = @my_left + 1 WHERE lft = orig_left AND rgt = 0 ;
       
          SET @my_left = @my_left + 1;
       
      END LOOP;
      CLOSE cursor1;
  END; ~~

  DELIMITER ;

And here's the results:

  mysql> SELECT CONCAT( REPEAT( ' ', (COUNT(parent.language) - 1) ), node.language) AS name FROM language_family_mptt AS node, language_family_mptt AS parent WHERE node.lft BETWEEN parent.lft AND parent.rgt GROUP BY node.language ORDER BY node.lft;
  +---------------------------------+
  | name                            |
  +---------------------------------+
  |    Finno-Ugric                  |
  |        Baltic-Finnic            |
  |            Estonian             |
  |                South Estonian   |
  |                    Voro         |
  |            Finnish              |
  |            Ingrian              |
  |            Karelian             |
  |                Karelian Proper  |
  |                Lude             |
  |                Olonets Karelian |
  |            Livonian             |
  |            Veps                 |
  |            Votic                |
  |        Hungarian                |
  |        Khanty                   |
  |        Mansi                    |
  |        Mari                     |
  |        Mordvinic                |
  |            Erzya                |
  |            Moksha               |
  |        Permic                   |
  |            Komi                 |
  |            Komi-Permyak         |
  |            Udmurt               |
  |        Sami                     |
  |            Eastern Sami         |
  |                Akkala Sami      |
  |                Inari Sami       |
  |                Kemi Sami        |
  |                Kildin Sami      |
  |                Skolt Sami       |
  |                Ter Sami         |
  |            Western Sami         |
  |                Lule Sami        |
  |                Northern Sami    |
  |                Pite Sami        |
  |                Southern Sami    |
  |                Umi Sami         |
  +---------------------------------+
  39 rows in set (0.00 sec)

:D

Jpeg and WebP -- what's the diff?

I used Paint.NET's XOR blending to create a diff between the sample Jpeg and WebP images that google posted on their blog. Here's the result:


Click to see the full size image.

The colors you see on the diff image is where the two images had disagreements about what color the pixel was. Where it's white, the two images had the same color for that part.

Translation

My translation of Johann Gottfried Herder' classic poem:

Our life is but a dream, a dream
Here in this Earthly sphere
Like shadows on the wavecrest
we rise and disappear.

We mark our plodding journey
in Time and Space,
unknowingly
in the midst of eternity.

Outer joins have a (+)?

Oracle Joins have a weird syntax for outer joins. The table that shows null values has a (+) appended to it, IIRC. I don't know if this is ANSI syntax or Oracle's own. I suspect it's Oracles; whatever the case, I don't like it. It breaks the standard of SQL syntax being English words ( FROM, WHERE, LIKE ), instead of weird operator symbols.

What is dark matter?

Dark Matter is not an aether. It's a very simple proposition:

All dark matter does is weigh. It doesn't reflect light; it doesn't interact with any other particles. All it does is exert gravitational attraction. Now, think about that for a moment. Suppose such a stuff as dark matter, which only exerts gravitational attraction, but has no other observable phenomena, actually existed. How would we come to know about it? What phenomena would we be observing that would indicate the existance of such a stuff? Only one: mass -- and nothing else.

All that we know about the universe is that there is missing mass. We've measured all the mass from everything that can be observed and we've come up short. We've accounted for every 'thing' we can observe and it doesn't weigh enough. So therefore, there is something out there that weighs, but doesn't generate any other observable phenomena -- it doesn't emit light nor does it crash into anything. It just weighs. That's all it is -- weight alone.

Are we alone in the Universe? Yes, we are

Imagine a UFO lands in a football stadium. A humanoid creature walks out onto the field. A television reported breathlessly states, "Finally, proof that we are not alone in the universe!"

Microphones are raised to the creature. He begins, "Sadly, we are alone in the universe. Only humans and aliens exist -- just us two, and nobody else. We are alone."

What does it mean to be alone? Are 4 billion humans not enough for you? How many conscious beings does there need to be for us not to be alone? Enough so that the annihilation of a couple of suns or planets does not wipe out conscious life everywhere?