public function matchSymbol(Symbol $symbol)
{
if ($symbol instanceof EpsilonSymbol) {
return true;
}
if (EpsilonSymbol::singletonInstance()->getType() == $symbol->getType()) {
return EpsilonSymbol::singletonInstance()->toString() == $symbol->toString();
}
return false;
}
/**
* @return ExpressionSymbol
*/
public static function createAdapterForEpsilon()
{
$epsilon = new EpsilonSymbol();
return new self($epsilon->getType(), $epsilon->toString());
}
/**
* @param Symbol $nonTerminal
*
* @return bool
* @throws \Exception
*/
public function addEpsilon(Symbol $nonTerminal)
{
$terminalSet = $this->getTerminalSet($nonTerminal);
if (is_null($terminalSet)) {
throw new \Exception('no terminal set found for symbol ' . $nonTerminal->toString());
}
return $terminalSet->add(EpsilonSymbol::singletonInstance());
}
public function testComputeFromListOfNonTerminalsWhichDeriveEpsilon()
{
$nonTerminals = ['A_1' => StandardSymbol::nonTerminal('A_1'), 'A_2' => StandardSymbol::nonTerminal('A_2'), 'A_3' => StandardSymbol::nonTerminal('A_3'), 'A_4' => StandardSymbol::nonTerminal('A_4')];
$terminals = ['b_1' => StandardSymbol::terminal('b_1'), 'b_2' => StandardSymbol::terminal('b_2'), 'b_4' => StandardSymbol::terminal('b_4')];
$parseSets = ['A_1' => [EpsilonSymbol::singletonInstance(), $terminals['b_1']], 'A_2' => [EpsilonSymbol::singletonInstance(), $terminals['b_2']], 'A_3' => [EpsilonSymbol::singletonInstance()], 'A_4' => [EpsilonSymbol::singletonInstance(), $terminals['b_4']]];
$sentence = 'A_2 A_2 A_1 A_3 A_4';
$expectedSet = new ArraySet();
$expectedSet->add($terminals['b_1']);
$expectedSet->add($terminals['b_2']);
$expectedSet->add($terminals['b_4']);
$epsilon = EpsilonSymbol::singletonInstance();
$expectedSet->add($epsilon);
$actualSet = $this->buildFirstSet($sentence, $parseSets, $nonTerminals, $terminals);
$this->assertEquals($expectedSet->count(), $actualSet->count(), 'unexpected number of actual items found');
/** @var Symbol $symbol */
foreach ($actualSet as $symbol) {
$contains = $expectedSet->contains($symbol);
$this->assertTrue($contains, sprintf('Symbol %s not found', $symbol->toString()));
}
}
