And if it sees S-W-A-P, open parentheses, close parentheses, and it hopefully sees two ints inside of it, that's all it needs to do in order to finish compiling your code.

如果它看到了SWAP，左圆括号，右圆括号，它可能载里面看到两个int数，那是它所需要做的,用来完成代码的编译。

哈佛公开课 - 计算机科学课程节选