rotfl
e^x and a constant were walking down the street. Suddenly, the constant notices a differential operator walking along the other side of the street. "Oh, no!" exclaims the constant. "I've got to run away! You've got to hide me! There's a differential operator... he could reduce me to nothing!" "Hmmmph," came the haughty reply. "I'm e^x. He can't do anything to me." So e^x walked across the street and introduced himself. "Hi. How are you doing? I am e^x," he bragged. "Pleased to meet you," replied the differential operator. "I'm d/dy."