再请教so ...as to和so as to区别和用法

关于so ...as to和so ...that的区别，很多nn的帖子已经说得很明白了，但是我还不是特清楚so ... as to和so as to的区别？

so ...as to do, 表示如此...以至于...

so as to = in order to...  为了..的目的

不知道我上面的理解是否正确，请指教！

论坛里有很多关于so that 和so as to的帖子，但是大多都是一些讨论贴，看得我头都晕了。在实战中so that, so as to 都可能作答案。比较，肯定的是，两者表示如此...以至于...:so...that结构中，that可以有自己的逻辑主语，so...as to必须保持逻辑主语和主语一致。请NN指教。

so as to对应结构简单，主谓单一的句子，就是说这个词组的主语就是整个句子的主语。后面不能接句子

so that后可接不同的主语就是可以接一个句子

MM找了两道关于so..as to的 OG例题，没看到有专门考so as to ,so...as to区别的，主要是和so that混在一起考逻辑主语是否一致的：

67. Congress is debating a bill requiring certain employers provide workers with unpaid leave so as to care for sick or newbom children.

(A)  provide workers with unpaid leave so as to

(B)  to provide workers with unpaid leave so as to

(C)  provide workers with unpaid leave in order that they

(D)  to provide workers with unpaid leave so that
                they can

(E)  provide workers with unpaid leave and

Choices A, C, and E are ungrammatical because, in this context, requiring ... employers must be followed by an infinitive. These options display additional faults: in A,
                            so as to fails to specify that the workers receiving the leave will be the people caring for the infants and children(清晰);
                in order that they, as used in C, is imprecise and unidiomatic; and E says that the bill being debated would require the employers themselves to care for the children. Choice B offers the correct infinitive, to provide, but contains the faulty so as to. Choice D is best.

So as to 的主语应该是谓语动作的发出者，即employers

So that 的主语可以是宾语
                （注意反例！）

88. The Emperor Augustus, it appears, commissioned an idealized sculpture portrait, the features of which are so unrealistic as to constitute what one scholar calls an "artificial face."

(A)  so unrealistic as to constitute

(B)  so unrealistic they constituted

(C)  so unrealistic that they have constituted

(D)  unrealistic enough so that they constitute

(E)  unrealistic enough so as to constitute

The verbs are and calls indicate that the sculpture is being viewed and judged in the present. Thus, neither the past tense verb constituted (in B) nor the present perfect verb have constituted (in C) is correct (1. 主从句中时态的呼应是gmat经常考点之一；2. 感觉逻辑主语对的时候，用so as to 比so that要更简洁)，何况这而用完成时没道理; both suggest that the statue's features once constituted an artificial face but no longer do so. Also, B would be better if that were inserted after so unrealistic, although the omission of that is not ungrammatical. Choices D and E use unidiomatic construc­tions with enough: unrealistic enough to constitute would be idiomatic, but the use of enough is imprecise and awkward in this context(用词的准确性). Choice A, which uses the clear, concise, and idiomatic construction so unrealistic as to constitute, is best.

对比103题

So …as to 与so… that 的区别是前者的主语都是谓词的主语，是固定的。后者可以通过that 从句调整后半句的主语，但是遇到单一主语（本题）就显得罗嗦了。

103. Students in the metropolitan school district lack math skills to such a large degree as to make it difficult to absorb them into a city economy becoming ever more dependent on information-based industries.

(A)  lack math skills to such a large degree as to make it difficult to absorb them into a city economy becoming

(B)   lack math skills to a large enough degree that they will be difficult to absorb into a city's economy that becomes

(C)   lack of math skills is so large as to be difficult to absorb them into a city's economy that becomes

(D)  are lacking so much in math skills as to be
                difficult to absorb into a city's economy
                becoming

(E)   are so lacking in math skills that it will be difficult
                to absorb them into a city economy becoming

In A, lack is modified by a wordy and awkward construction, to such a large degree as to make it difficult to(和用so that 比起来，这个修饰确实不清晰，也不简洁). B is similarly flawed, and to a large enough degree that is unidiomatic. C is ungrammatical because it uses lack as a noun rather than as a verb: the phrase beginning Students... becomes a dangling element, and them refers illogically to skills rather than students(of 连接的词都是名词性的).
                Additionally, A, B, and C fail to use one or both of the "-ing" forms are lacking and becoming; these forms are preferable to lack and becomes in describing progressive and ongoing conditions. D uses the "-ing" forms, but so much... as to be difficult to absorb is an awkward and unidiomatic verbal modifier. Choice E is best.

Enough : 感觉一般说正面的事情，比如large enough to accommodate …

Such … as to : 后面如果要说被动和形容词就会显得wordy, such的主语是谓词的主语（在A里面就是students）

So … as to : D  students are lacking so … as to be difficult to … 因为so … as to 的主语都是谓词的主语所以as to后面的意思成了 students be difficult to…

So that: 在需要说形容词（事情状态 it is difficult）的时候,因为可以自由加主语，更好。

比较88题