Created
January 26, 2011 03:23
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A simple scanner that uses regular expressions to parse strings
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<?php | |
class Scanner | |
{ | |
private $_scans; | |
private $_idx; | |
public function __construct(array $scans) | |
{ | |
$this->_scans = array(); | |
foreach ($scans as $regex => $callback) { | |
$regex = '/(^' . $regex . ')/'; | |
$this->_scans[$regex] = $callback; | |
} | |
} | |
public function scan($str) | |
{ | |
$idx = 0; | |
$cont = true; | |
do { | |
$cont = false; | |
foreach ($this->_scans as $regex => $callback) { | |
$matches = array(); | |
if (preg_match($regex, substr($str, $idx), $matches)) { | |
$idx += strlen($matches[0]); | |
if (is_callable($callback)) { | |
call_user_func($callback, $this, $matches[0]); | |
} | |
$cont = true; | |
break; | |
} | |
} | |
} while ($cont); | |
// Was this successfully parsed? | |
return ($idx === strlen($str)); | |
} | |
} | |
// if __name__ == "__main__": | |
if (!debug_backtrace()) { | |
class Tokenizer | |
{ | |
public $tokens; | |
public function __construct() | |
{ | |
$this->tokens = array(); | |
} | |
public function identifier(Scanner $scanner, $token) | |
{ | |
$this->tokens[] = "(IDENT, $token)"; | |
} | |
public function operator(Scanner $scanner, $token) | |
{ | |
$this->tokens[] = "(OPERATOR, $token)"; | |
} | |
public function digit(Scanner $scanner, $token) | |
{ | |
$this->tokens[] = "(DIGIT, $token)"; | |
} | |
public function endStmnt(Scanner $scanner, $token) | |
{ | |
$this->tokens[] = 'END_STATEMENT'; | |
} | |
} | |
$tokenizer = new Tokenizer; | |
$scanner = new Scanner( | |
array( | |
'[a-zA-Z_]\w*' => array($tokenizer, 'identifier'), | |
'[+\-*=]' => array($tokenizer, 'operator'), | |
'[0-9]+(\.[0-9]+)?' => array($tokenizer, 'digit'), | |
';' => array($tokenizer, 'endStmnt'), | |
'\s+' => null | |
) | |
); | |
$res = $scanner->scan('foo = 5.5 * 30; bar = bar - 60;'); | |
if ($res) { echo "TRUE\n"; } else { echo "FALSE\n"; } | |
echo join("\n", $tokenizer->tokens); | |
} |
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