Is there enough lunch for everyone to have a picnic together ? 

网友的句子，是不定式用在enough 之后作“结果状语”。只是在不定式前面加了一个逻辑主语for everyone，这样就是动词不定式复合结构，作“结果状语”

不定式的主要语法功能，是作目的状语和定语，但是不定式作结果状语也比较常见。不定式表示结果，经常用在以下结构中：

1. too...to...

He is too excited to say anything.

他激动得说不出话来。

The bag is too heavy for me to carry.

这个袋子太重，我提不动。

2. enough...to...

Is that room big enough to seat all of us？

那个房间足够大能容得下我们所有的人吗？

He was brave enough to do what he did. 

他足够勇敢以至于做了此事。

3. so...as to...

We have got so plenty of food as to treat our guests.

我们有如此充裕的食物来招待我们的客人。

He was so brave as to do what he did.

他如此勇敢以至于做了此事。

4. such...as to...

He was such a brave man as to do what he did.

他是如此勇敢的人以至于做了此事。

He is such a timid man as to be afraid of mice.

他是个如此胆小的人，以至于害怕老鼠。

5.表示出人意料的结果，不定式前常加上only：

She hurried to the station only to be told the train had gone.

她匆忙赶到车站却被告知火车已走了。

He hurried to that house only to find nobody in.

他急忙赶到那所房子，却发现空无一人。

6. 用在其他情况下：

（1）He lived to see his grandson married. 

他活到看到自己的孙子结婚。

（2）It seems that the employee didn't sleep at all to be so sleepy in the early morning.

好像这位雇员（晚上）根本没睡觉，才一大早这么困倦的。

（3）He looked both ways to find that nothing was coming, and then drove across without stopping completely.

他朝着两个方向看了看，结果没有发现什么东西过来，然后开车过去，全然没有停下来的意思。