"I have five pounds. Is that enough?"

"No."

"It costs more than five pounds?"

"No."

"How much do I have to pay?"

"This is NaN pounds."

"That means it costs more than five pounds?"

"No."

"It costs less than five pounds?"

"No."

"Exactly five pounds?"

"No."

leaves the shop

(Remember, comparison with NaN is always false)