The single quotation mark in front of the null list is used to tell Scheme that you are using as data and not as a part of your parse tree.

空列表前面的单引号用来告诉scheme您正在使用作为数据，而不是用它作为解析树的一部分。

youdao

Its most followed user, Mark Zuckerberg, now has more than 250, 000 followers, despite not Posting a single public item on his Google + account.

Google +上拥有粉丝最多的用户——马克·扎克伯格——现在已经拥有超过25万个粉丝，尽管他从来没在他的Google +账户上公开发布一条消息。

youdao

Kao Sung-nien's fat but firm face was like an unleavened millet-flour steamed bread. "Voracious time" (Edax vetustas) could not make a dent on it. There was not a single tooth mark or crease .

高校长肥而结实的脸像没发酵的黄面粉馒头，“馋嘴的时间”咬也咬不动他，一条牙齿印或皱纹都没有。

youdao

I used this product my entire pregnancy, almost every day. I did not have a single stretch mark the entire time.

整个怀孕期间，几乎每天使用这个产品，没有出现过一条妊娠纹。

youdao

I used this product my entire pregnancy, almost every day. I did not have a single stretch mark the entire time.

整个怀孕期间，几乎每天使用这个产品，没有出现过一条妊娠纹。

youdao