半杯水是什么哩？
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.
对于乐观主义者，这玻璃杯有一半是满的； 对于悲观主义者，这玻璃杯有一半是空的； 对于工程师，这玻璃杯比实际需要打了一倍。