A bunch of functions are sitting in a restaurant when suddenly, a crazy masked operator bursts in the door.
"I'm here to rob this place and I'm going to start differentiating all y'all if you don't leave right now!"
All the functions make a run for the door, except one sitting in a booth near the back. The operator notices this and says "Hey, didn't you hear me? I'll differentiate you til there ain't nothin' left!"
The function in the back smiles, "Go ahead, I'm e^x."