1. 不定式 to do 做主语时表一次性动作的例子：

To destroy 121 enemy aircraft is no mean record.  歼灭121架敌机是一个了不起的纪录。

To force this agreement on the nation is wrong. 把这份协定强加给这个国家是错误的。

To sign away his rights to the book would have been the height of folly. 他签字放弃著作权真是愚蠢之极。

To deprive the boy of his education is a violation of state law. 剥夺这个男孩受教育的权利是一种违反国家法律的行为。

注意有时使用形式主语。如：

It’s very important to remember this. 记住这一点很重要。

It's a pity to leave so early. 这么早走太遗憾。

It hurts me not to have been invited. 没有邀请我, 我很不痛快。

2. 不定式 to do 做主语时表示多次性动作的例子：

To have made the same mistake twice was unforgivable. 两次犯同样的错误是不可原谅的。

但更多情况不是直接表示多次动作，而是表示一种经常性的情况（指一直如此或通常如此，其中暗示多次动作）。如：

To cut taxes would probably do the economy more harm than good. 减税对经济而言可能弊大于利。

To keep your bearings in a desert sandstorm is impossible. 在沙漠的尘暴中要想保持方位感是不可能的。

To listen to someone is the greatest compliment you can pay. 用心倾听对方说话就是对别人最高的尊重。