对编译原理有兴趣的进解决方法

include 'ttrie.php';

class Rule extends TTrie {
  public $rule = array();
  public $savematch = 0;

  function __construct($s='') {
	$this->set( array(
		' ' => 'Separated',
		"\r\n" => 'set_rule',
		"\n" => 'set_rule',
		"\t" => 'Separated',
		'->' => 'Separated',
		'→' => 'Separated',
		'|' => 'set_parallel_rule',
		));
	$this->match($s);
	if($this->rule[0][0] == $this->rule[0][1]) {
		if(count($this->rule[0]) == 2) $this->rule[0][0] .= "'";
		else array_unshift($this->rule, array($this->rule[0][0]."'", $this->rule[0][0]));
	}else {
		$c = $this->rule[0][0];
		$n = 0;
		foreach($this->rule as $r) if($r[0] == $c) $n++;
		if($n > 1) array_unshift($this->rule, array($this->rule[0][0]."'", $this->rule[0][0]));
	}
  }
  function Separated() {
  }
  function set_rule() {
	$this->rule[] = $this->buffer;
	$this->buffer = array();
  }
  function set_parallel_rule() {
	$t = $this->buffer[0];
	$this->set_rule();
	$this->buffer[] = $t;
  }
}


class Grammar {
  var $closure = array();
  var $first = array();
  var $follow = array();
  var $rule = array();
  var $identifier = array();
  var $leay = array();
  var $forecast = array();
  var $stack = array();
  var $ll = 'LL(0)';
  var $lr = 'LR(0)';

  function __construct($s='') {
	$p = new Rule($s);
	$this->rule = $p->rule;
	$this->set_grammar();
  }

  function set_grammar() {
	foreach($this->rule as $rule) {
		if(! in_array($rule[0], $this->identifier)) $this->identifier[] = $rule[0];
	}
	foreach($this->rule as $rule) {
		foreach($rule as $v)
			if(! in_array($v, $this->identifier) && ! in_array($v, $this->leay))
				$this->leay[] = $v;
	}
	$this->set_first();
	$this->set_follow();
	$this->set_closure();
	$this->set_select();
	$this->set_forecast();
  }
  function set_first() {
	foreach($this->rule as $rule) $this->first[$rule[0]] = array();
	//直接收取 形如U->a…的产生式（其中a是终结符），把a收入到First(U)中
	foreach($this->rule as $v) {
		if(in_array($v[1], $this->leay)) $this->first[$v[0]][] = $v[1];
	}
	//反复传递 形入U->P1P2P3…Pn的产生式（其中P是非终结符），应先把First(P1)中的全部内容传送到First(U)中,如果P1中有ε，把First(P2)中的内容传送到First(U)中,类推直到Pi中无ε
	do {
		$t = serialize($this->first);
		foreach($this->rule as $rule) {
			for($i=1; $i				$v = $rule[$i];
				if(in_array($v, $this->identifier)) {
					$this->first[$rule[0]] = array_unique(array_merge($this->first[$rule[0]], $this->first[$v]));
					if(! in_array('#', $this->first[$v])) break;
				}else break;
			}
		}
	}while($t != serialize($this->first));
  }
  function set_follow() {
	foreach($this->rule as $rule) $this->follow[$rule[0]] = array();
	//直接收取 形如 …Ua… 的，把a直接收入到Follow(U)中
	foreach($this->rule as $rule) {
		for($i=1; $i			if(in_array($rule[$i], $this->identifier) && in_array($rule[$i+1], $this->leay))
				$this->follow[$rule[$i]][] = $rule[$i+1];
		}
		if(in_array($rule[$i], $this->identifier)) $this->follow[$rule[$i]][] = '#';
	}
	foreach($this->follow as &$v) if(! $v) $v[] = '#';
	//直接收取 形如 …UP…(P是非终结符)的，把First(P)中非ε收入到Follow(U)中
	foreach($this->rule as $rule) {
		for($i=1; $i			if(in_array($rule[$i], $this->identifier) && in_array($rule[$i+1], $this->identifier)) {
				$this->follow[$rule[$i]] = array_unique(array_merge($this->follow[$rule[$i]], array_diff($this->first[$rule[$i+1]], array('#'))));
			}
		}
	}
	//反复传递 形如U－>aP的(P是非终结符)或U->aPQ(P,Q为非终结符且Q中含ε)，应把Follow(U)中的全部内容传送到Follow(P)中
	do {
		$t = serialize($this->follow);
		foreach($this->rule as $rule) {
			$s = $rule[0];
			$d = end($rule);
			if(in_array($d, $this->leay)) continue;