function parse_factor()
{
switch ($this->peek()) {
case 'leftparen':
$this->next();
$a = $this->parse_alternates();
$this->parse_terminal('rightparen');
return $a;
case 'token':
$t = $this->parse_terminal('token');
$n = new enfa();
$n->recognize($t);
return $n;
case 'epsilon':
$t = $this->parse_terminal('epsilon');
$n = new enfa();
$n->add_epsilon($n->initial, $n->final);
return $n;
}
die('CFG/PG got stuck parsing factors.');
}
function nfa_concat($nfa_list)
{
$out = new enfa();
$last_state = $out->initial;
foreach ($nfa_list as $nfa) {
$out->copy_in($nfa);
$out->add_epsilon($last_state, $nfa->initial);
$last_state = $nfa->final;
}
$out->add_epsilon($last_state, $out->final);
return $out;
}