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

My prototype, again, so that I can use it later increment without the compiler wondering what is this increment that you're referring to because it's not otherwise been declared.

我的函数原型，再次强调，我可以以后使用它,这样编译器就不会疑惑这个你提及的,是什么，因为是没有,被声明的。

哈佛公开课 - 计算机科学课程节选