/**
* @param string $stringSymbol
* @return ExpressionSymbol
*/
public function createTerminal($stringSymbol)
{
if ($stringSymbol === '') {
return ExpressionSymbol::createAdapterForEpsilon();
}
return ExpressionSymbol::createAdapterForTerminal($stringSymbol);
}
protected function addEpsilonAlternativeForItem(Symbol $nonTerminal, Expression $optionalExpression)
{
$alternationItems = array(ExpressionSymbol::createAdapterForEpsilon());
if ($optionalExpression instanceof Concatenation) {
$alternationItems[] = $optionalExpression;
} elseif ($optionalExpression instanceof Choice) {
$alternationItems[] = new Group($optionalExpression);
} else {
$alternationItems[] = $optionalExpression;
}
$alternation = new Choice(array_shift($alternationItems), $alternationItems);
$production = new StandardProduction($nonTerminal, $alternation);
$this->epsilonAlternatives[] = $production;
return $production;
}
