/**
* Get an Instance of ExpressionManufacturer
*
* @return ilAssLacExpressionManufacturer
*/
public static function _getInstance()
{
if (self::$instance == null) {
self::$instance = new ilAssLacExpressionManufacturer();
}
return self::$instance;
}
/**
* Manufacure an expression from the delivered node and the index. If an expression already exist in the node for<br />
* for the delivered index, this function will return the existing expression
*
* @param array $node
* @param int $index
*
* @return ilAssLacCompositeInterface
*/
private function getExpression(array $node, $index)
{
$manufacturer = ilAssLacExpressionManufacturer::_getInstance();
$expression = $node['nodes'][$index];
if (!$expression instanceof ilAssLacAbstractComposite) {
$expression = $manufacturer->manufacture($node['nodes'][$index]['value']);
}
return $expression;
}
/**
* Cannonicalize the condition into a more general form. <br />
* It replaces all expression with "n" and all orperators with "o" <br />
* so that the result of an condition after cannonicalization could be:<br />
* <br />
* (n o n) o (n o n) o n
*/
protected function cannonicalizeCondition()
{
$manufacturer = ilAssLacExpressionManufacturer::_getInstance();
$this->condition = preg_replace($manufacturer->getPattern(), 'n', $this->condition);
$manufacturer = ilAssLacOperationManufacturer::_getInstance();
$this->condition = preg_replace($manufacturer->getPattern(), 'o', $this->condition);
$this->condition = preg_replace("/no/", "n o", $this->condition);
$this->condition = preg_replace("/on/", "o n", $this->condition);
for ($i = 0; $i < strlen($this->condition); $i++) {
if ($this->condition[$i] == "!" && !$this->isNegationSurroundedByBrackets($i)) {
$this->surroundNegationExpression($i);
}
}
}
