当你在买这些东西上省钱时，每个折扣只有一次使用机会。

When you save money on these purchases, each discount only happens once.

youdao

此模式将文件划分为记录，并使用每个记录进行一次服务调用，或将消息传递到具有事务接口的一个或多个系统。

This pattern breaks a file down into records and USES each record to make a service call, or pass a message to one or more systems with a transactional interface.

youdao

通过使用缓存代理，每个页面都只需从门户交付一次，然后此页面将驻留在缓存中(直到内容无效时为止)。

By using caching proxies, each page would be delivered from the portal only once and then reside within the cache (until the content becomes invalid).

youdao

That one's not so obvious. So let's think about this for a second. To sort a list in linear time, would say, I have to look at each element in the list at most a constant number of times.

所以让我们来思考一会,要在线性时间能排序，列表里每个元素最多被使用常数次,不一定是一次，对吧。

麻省理工公开课 - 计算机科学及编程导论课程节选