用动词不定式做目的状语可以忽略句子主语吗
用动词不定式做目的状语不可以忽略句子主语。
It's important to use dictionaries in learning a foreign language.
It's important to use dictionaries to learn a foreign language.
It's important to use dictionaries for learning a foreign language.
以上几个句子中，to use是真正主语。in learning, to learn, for learning作状语都是修饰不定式to use的，而不是句子的目的状语。不定式或介词+动名词修饰另一个动词（谓语或者非谓语），不定式或动名词的逻辑主语应该是被修饰名词的施事者。在本句中，to use的逻辑主语是谁，to learn或learning的逻辑主语就是谁。
不定式作谓语动词的目的状语时，通常其逻辑主语应该是句子的主语。但如果不定式就是的是非谓语动词，其逻辑主语就不一定是句子的主语，而是那个动词的施事者。
不定式和不定式短语作目的状语：
不定式和不定式短语作目的状语,主要用来修饰动词,表示某一动作或状态的目的.为了使目的意义更加清楚或表示强调意义时,还可以在前面加in order to或so as to.例如：
I've written it down in order not to forget.
He shouted and waved so as to be noticed.
在句子中作谓语动词的状语的不定式或不定式短语,表示的是主语的目的,因此,其逻辑主语通常是句子的主语.比较：
To draw maps properly,you need a special pen.(正)
To draw maps properly,a special pen is needed.(误)
由in order to引导的目的状语,既可以置于句尾,也可以置于句首,而由so as to引导的目的状语,只能置于句尾,而不能置于句首.比较：
They started early in order to get there in time.(正)
In order to get there in time,they started early.(正)
They started early so as to get there in time.(正)
So as to get there in time,they started early.(误)
