public function diff( Snapshot $other ) {

		return new self(
			$this->_time - $other->getTime(),
			$this->_memoryUsage - $other->getMemoryUsage(),
			$this->_realMemoryUsage - $other->getRealMemoryUsage(),
			( $this->_memoryUsagePeak + $other->getMemoryUsagePeak() ) / 2,
			( $this->_realMemoryUsagePeak + $other->getRealMemoryUsagePeak() ) / 2
		);
	}