It's adj for sb to do【形式主语】和To do sth is adj to sb【动词不定式子做主语】
那两个句型是一样的，只是把句子构造变形罢了。
to meet his girlfriend unexpectedly was surprise
it was surprise for his girlfriend to meet
翻译（translate）：不期而至的相遇令他十分惊讶
To do sth is adj for sb那个句子构造式能够的【动词不定式做主语】
例如（such as):to take a course in the college is so humdrum for me【动词不定式做主语】
翻译（translate）：去大学里面听课关于我来说是一件如斯无聊的工作。
to sb 和for sb都能够,没什么差别,都是“对某人来说怎么样”的意思，趁便给你提个醒，当用It is adj for sb to do sth时，若是描述词是描写人品量的一类词时就不消for而要用of.如It is kind/good/nice of you to help me.
能够。
It's adj for sb to do和To do sth is adj for sb两个句子素质上是一样的，前一个是用了it取代后面的to do sth
0