public function parseInputStreamWithBacktracking(InputStreamInterface $input, ExpressionResultInterface $previous_result = null)
{
/** @var AlternativeExpressionResult $previous_result */
if ($previous_result !== null && $previous_result instanceof AlternativeExpressionResult === false) {
throw new \Exception("Expected " . AlternativeExpressionResult::class);
}
$alternatives = $this->alternatives;
/** @var BacktrackingStreamingParserInterface|false $current_alternative */
$current_alternative = reset($alternatives);
$active = $previous_result === null;
while ($active === false) {
$active = key($alternatives) === $previous_result->getKey();
if ($active === true) {
$alternative_result = $current_alternative->parseInputStreamWithBacktracking($input, $previous_result->getResult());
if ($alternative_result !== null) {
return new AlternativeExpressionResult($alternative_result, key($alternatives));
}
}
$current_alternative = next($alternatives);
}
while ($current_alternative !== false) {
$current_alternative = current($alternatives);
$alternative_result = $current_alternative->parseInputStreamWithBacktracking($input);
if ($alternative_result !== null) {
if ($previous_result !== null && $previous_result->getLength() === $alternative_result->getLength()) {
return null;
}
return new AlternativeExpressionResult($alternative_result, key($alternatives));
}
$current_alternative = next($alternatives);
}
return null;
}
public function getLength()
{
return $this->part_result->getLength();
}
