class ChainElement

abstract class ChainElement extends Node implements Expression {
    protected $propertiesMap = array(
        "optional" => false,
    );
    
    /**
     * Optional flag that is true if the node is in the optional
     * part of a chain expression
     *
     * @var bool
     */
    protected $optional = false;
    
    /**
     * Returns the optional flag that is true if the node is in
     * the optional part of a chain expression
     *
     * @return bool
     */
    public function getOptional() {
        return $this->optional;
    }
    
    /**
     * Sets the optional flag that is true if the node is in
     * the optional part of a chain expression
     *
     * @param bool $optional Optional flag
     *
     * @return $this
     */
    public function setOptional($optional) {
        $this->optional = (bool) $optional;
        return $this;
    }

}