for sb to do sth用作主语

for sb to do sth在句子中可有作主语。如：

For you to ask Joe would be a big mistake. 你要是去问乔，那将是一大错误。

For Ann to go to France would make me very happy. 安要是到法国去将使我感到很高兴。

注：这类结构通常会借助形式主语来表达，即在句首使用形式主语，而将真正用作主语的“for+宾语+不定式”结构移至句末。如：

It’s too expensive for me to buy. 太贵了，我买不起。

It’s impossible for me to leave my family. 我是不可能离开家的。

It’s impossible for the job to be finished in time. 这项任务要按时完成是不可能的。

It’s an honour for me to be asked to speak here. 我很荣幸被邀在这里讲话。

It’s a new experience for her to be travelling by plane. 坐飞机对她是—次新经历。

It’ll take time for her to recover from the illness. 她的病要很长时间才能痊愈。

It took twenty minutes for the smoke to clear. 过了20分钟烟才散完。