市场上也有20个店左右的连锁，但是他们的期望值也很高。

There also is the chain that 20 inns control on the market, but their expectation cost is very high also.

youdao

So you're implementing this black box, and if its purpose in life is to actually return a value, you have to tell the compiler what kind of value to expect, and this is going to have ripple effects.

你在实现这个黑盒子，如果它的目的是,返回一个值，你必须告诉编译器你期望的是什么类型的值，这个将是一个连锁反应。

哈佛公开课 - 计算机科学课程节选