The Liskov Substitution Principle is a fundamental concept in object-oriented programming, stating that objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.

The whole of life is just like watching a film. Only it's as though you always get in ten minutes after the big picture has started, and no-one will tell you the plot, so you have to work it out all yourself from the clues.

国与国之间是平等的，人与人之间也是平等的，在人格与尊严上是没有贵贱之分的，上天对所有人都是一视同仁的，人生而平等是上天赋予每个人的不可被侵犯的权利。

高尔夫是一项讲究尊重和体育精神的运动——我们必须尊重它的传统和行为准则。

数学思想的美丽之处在于它可以跨越文化和时间被分享和理解。