If the roll forward set has not been rolled forward far enough to be consistent with the database, the undo phase cannot occur.

如果前滚集前滚得不够远，无法与数据库一致，则不会出现撤消阶段。

youdao

Here,he uses a set of buttons attached to a computer to make the silent robot move forward, backward or around in circles.

VOA: special.2009.12.17

And one of the things that was useful here is, that we actually know that the set of primitives that you want to use is very straight-forward.

这儿有一个很有用的东西是，我们实际知道你想用的,一系列基本类型是非常明显的。

麻省理工公开课 - 计算机科学及编程导论课程节选

The problems are set up so that, if you start down the right path, it should be pretty straight-forward to work it through If you start down a plausible but incorrect path, you can sometimes find yourself stuck in the weeds somewhere, and we want to bring you back in.

问题提出了，如果你从，一开始就走正确的道路，解决的途径,就一目了然了,如果你走上一条貌似正确但实际错误的道路，你会在某时某刻,发现自己陷入泥沼，于是我们就会把你拉回来。

麻省理工公开课 - 计算机科学及编程导论课程节选

Jose Angel Valdes was sent off for a second booking with 10 minutes left after Alvaro Negredo went down clutching his face, and the Sevilla forward set up defender Cala from the resulting free-kick.

CNN: STORY HIGHLIGHTS

In addition, the diminutive forward set a new record for the European Champions League by scoring 14 goals during the 2011-12 campaign, a period when he became the first man to score five goals in a game in the competition (against Bayer Leverkusen).

CNN: Messi crowned world's best for record fourth time

He recently put forward a set of ideas that Congress could act on that build on the measures he proposed last fall.

WHITEHOUSE: Press Briefing