作主语用There being…还是There to be…

There ______ a swimming pool in our school is what we expect.

是填 being 还是 to be，或是两者都可以？为何？

以下两个句子都正确（is 前面都是主语，但 being 不可以与for连用，to be需要与for连用）：

There being aswimming pool in our school is what we expect.

For there to be a swimming pool in our school is what we expect.

例句：

There being an index to this dictionary is a great advantage. 这本词典有索引非常便利。

For there to be so few students in the reading room was unusual. 阅览室里只有这么几个学生是少有些。