extracting from a string

[garrensilverwing]

to try and speed up the process of adding chess games to my website i would like a piece of code that will search a large string for certain bits of information, so instead of hand typing them into the database every time i could just enter the string and it will do the job for me. here is an example of what i want to do:

[Event "Wyoming Open"]
[Site "Laramie College"]
[Date "2006.05.06"]
[Round "3"]
[White "James Kulbacki"]
[Black "Chris Peterson"]
[Result "0-1"]
[ECO "A00"]
[WhiteElo "1880"]
[BlackElo "1668"]
[PlyCount "38"]
[EventDate "2006.??.??"]
[TimeControl "35/90:0"]

1. b4 e5 2. Bb2 Bxb4 3. f4 Nc6 4. fxe5 f6 5. exf6 Nxf6 6. Nf3 O-O 7. g3 Ng4 
8.c3 Bc5 9. d4 Qe7 10. Qd3 d5 11. dxc5 Bf5 12. Qxd5+ Kh8 13. Nbd2 Rad8 
14. Qb3 Qe3 15. c4 Qf2+ 16. Kd1 Rxd2+ 17. Kxd2 Rd8+ 18. Kc1 Ne3 
19. Nd2 Qe1+ 
0-1

this is a PGN format chess game. i need to extract the first and last names (seperately) for both white and black, both their ratings, the ECO, the result and the year. the rest of the information can be discarded. I have no idea how to do this and tutorials online are not very helpful so thanks in advance

[garrettroyce]

$strings = explode('[', $string); //every time a [ is encountered, a new string is added to the array $strings
$white = substr($strings[4], 6, -2); // white is the 4 element (from zero), name starts after 7th char (from zero) remove last 2 chars "]
$white_first = strstr($white, ' '); // get everything before and including the first space in white's full name
$white_last = substr($white, strlen($white_first)); // get everything after the first space in white's full name
$white_first = substr($while, 0, -1); // remove the last char (space) from white's first name
$white_rating = substr($strings[8], 9, -2); // white's rating is 8th from zero string, starts after 9 chars, drop last 2 chars
$result = substr($strings[6], 9, -2); // you get the picture by now :)
$year = substr($strings[11], 11, 4); // year is always 4 chars long

I'll leave black up to you, I'm going to bed :P

[misson]

Regular expressions are the easiest way to do it, though REs can be hard to learn. Studying the relationship between regular languages and finite state machines will give you the best understanding. You could also try MDC RE guide or the Perl RE tutorial

For example, /\[(White|Black) ".* ([A-Za-z']+)"\]/ will match and extract the player's color and last name. What language do you want to use to translate the data?

[garrensilverwing]

Regular expressions are the easiest way to do it, though REs can be hard to learn. Studying the relationship between regular languages and finite state machines will give you the best understanding. You could also try MDC RE guide or the Perl RE tutorial

For example, /\[(White|Black) ".* ([A-Za-z']+)"\]/ will match and extract the player's color and last name. What language do you want to use to translate the data?

i was hoping to do it in php so i dont have to fiddle with any more types of code lol

[garrettroyce]

mission's answer is php code, it uses a more complex system. Regular expressions are extremely powerful, and even though the rules are simple, they are difficult to master. If you were to go mission's route, it will definitely be a good tool for you to use in the future, but it will take a lot of patience and learning. My route is very simple, but it takes more code to do the same thing.

[garrensilverwing]

well im not too worried about length of code right now because sometimes you have to do things the hard way first and im doing everything else the hard way and then converting it when i get it working which is probably an ass backwards way of doing it but i am learning so much

[misson]

To illustrate the utility of regular expressions, here are some example functions for this problem. pgn2array will turn a string containing PGN formatted pairs into an associative array.

function parseName($name) {
    preg_match('/^(?:(\S+) (?:(.*) )?)?(\S+)$/', $name, $name);
    return array_combine( array('full', 'first', 'middle', 'last'), $name);
}

function parseDate($date) {
    return array_combine(array('year', 'month', 'day'), explode('.', $date));
}

function pgn2array($pgn) {
  static $filters = array('white' => 'parseName', 'black' => 'parseName', 
                          'date' => 'parseDate', 'eventdate' => 'parseDate');
  $arr=False;
  if (preg_match_all('/\[(\w+) "([^"]+)"\]/', $pgn, $matches, PREG_PATTERN_ORDER)) {
      $arr = array_combine(array_map('strtolower', $matches[1]), $matches[2]);
      foreach ($filters as $key => $filter) {
          $arr[$key] = call_user_func($filter, $arr[$key]);
      }
  }
  return $arr;
} 

If the data is stored in a file, the above would require you to read the whole file before parsing it. To parse a file in place, try:

function filterTagPair($key, $value) {
    switch($key) {
    case 'white':
    case 'black':
        return parseName($value);
        break;
    case 'date':
    case 'eventdate':
        return parseDate($value);
        break;
    }
    return $value;
}

function pgnFile2array($file) {
    $arr = array();
    $fpos = ftell($file);
    while (!feof($file) && $line=fgets($file)) {
        if (preg_match('/\[(\w+) "([^"]+)"\]/', $line, $matches)) {
            $matches[1] = strtolower($matches[1]);
            $matches[2] = filterTagPair($matches[1], $matches[2]);
            $arr[$matches[1]] = $matches[2];
            $fpos = ftell($file);
        } else {
            fseek($file, $fpos);
            break;
        }
    }
    return count($arr) ? $arr : False;
} 

Looping over an array of filters (as pgn2array does) would work just as well for pgnFile2array. I used a switch to illustrate another approach.

None of the above deals with errors, so they could be fleshed out in this regard.

[xav0989]

well im not too worried about length of code right now because sometimes you have to do things the hard way first and im doing everything else the hard way and then converting it when i get it working which is probably an ass backwards way of doing it but i am learning so much

Well in this case, the hard way, regular expressions, is also the best way!

[misson]

As for the power of regular expressions, XKCD says it best:

[xav0989]

Nice one there, mission!