He can point out the male paradise whydah with its unusually long black tail feathers.

VOA: special.2009.08.19

So just to hammer home this point, for now, a function really is like a black box.

现在再三强调，让你们彻底了解这一点，一个函数就像是一个黑盒子。

哈佛公开课 - 计算机科学课程节选