The prime number detector is quite clever. It reminds me of the number based logic constructs from Godel's incompleteness theorem. It's essentially maps a mathe

The prime number detector is quite clever. It reminds me of the number based logic constructs from Godel's incompleteness theorem. It's essentially maps a mathematical concept to a string and operates on it. For any unary integer greater than 1, the regular expression /^(11+?)\1+$/ matches it iff the number is not a prime. In other words, if there exists no integer less than the number itself and greater than one (first capturing group) that is a divisor of the number. The non-greedy + is also a nice touch, it will start out from the smallest factors and build from there.