It's even worse if one of those calculations has side effects (like printing, modifying a global variable, etc.) because these side effects will be processed twice.
Pages to view: The number of pages on a printing plate, and therefore on oneside of a printed sheet .
版上页数：在印版上的页数，即是印刷纸张一面上的页数。
3
This correspondent has always believed in printing on both sides of paper and has been known to put paper printed on just oneside back into the office printer, upside down.