protected function reduce()
    {
        /** @noinspection PhpUndefinedMethodInspection */
        $gcd = $this->gcd($this->value['num']->get(), $this->value['den']->get());
        if ($gcd > 1) {
            $this->value['num']->set($this->value['num']->get() / $gcd) ;
            $this->value['den']->set($this->value['den']->get() / $gcd);
        }
    }