Are you happy to see each other?这句话中to 起什么作用 为什么不是for?

Are you happy to see each other?这句话中to 起什么作用 为什么不是for? They are happy to see each other happy they to each are see other 排句子 They are happy to see each other again. happy to see each other again We are going to see each other for the first time.为什么用for? 英语：We are very happy to be with each other.这句话中的to 连词成段（England):are,to,each,the,other,students,happy,see. happy,the,the,students,are ,to ,and,see,each,other,teachers, 连词成句并翻译成中文：to,each,their,friends,happy,are,see,other(.) happy ,see,again,to,other,they,each,are(连词成句） 用 happy we see to are other each again 连个句子