public function compile(ExpressionInterface $expression)
 {
     /** @var $expression \PeterVanDommelen\Parser\Expression\Constant\ConstantExpression */
     if (strlen($expression->getString()) === 1) {
         return new SingleByteParser($expression->getString());
     }
     return new ConstantParser($expression->getString());
 }
 public function isPotentiallyEmpty(ExpressionInterface $expression)
 {
     /** @var $expression \PeterVanDommelen\Parser\Expression\Constant\ConstantExpression */
     return $expression->getString() === "";
 }