表示"一…就…"的结构

hardly/scarcely…when/before, no sooner…than　和as soon as都可以表示"一…就…"的意思，例：

I had hardly / scarcely got home when it began to rain.

I had no sooner got home than it began to rain.

As soon as I got home, it began to rain.

注意：如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构：

Hardly / Scarcely had I got home when it began to rain.

No sooner had I got home than it began to rain.