would have done用法归纳高中
是一个固定虚拟语气的用法。
表示对过去事情的假设，意为“本来想做、要做但没做”，使用时大多会给出导致没做成或会这样做的条件。
If I had a chance，I would have set off on a journey round the world.
要是有机会，我早就环游世界了。
would have done与if连用
例句If I hadn’t been busy that day, I would have gone there with them.
如果那天我不忙，我会和他们一起去那儿。（事实上表示没有由于忙，而没有去。）
在这里也可以不用if
如I was busy that day. Otherwise I would have gone there with them.
我那天很忙，否则，我就和他们一起去那儿了。
