F-O-O in lowercase and, in fact, foo it is buggy because I typed lowercase F-O-O and FOO yet I get back capital F-O-O as both the original and the copy and that's simply because I haven't done this correctly.

小写的f-o-o，实际上，它是有bug的，因为我输入小写的,而我得到的原始的和拷贝的都是大写的,简单说，我处理错了。

计算机科学课程节选 : 哈佛公开课