Function to calculate prime numbers...uses !!!.

gistfile1.rb

  def prime_numbers(upper_bound)
    return [] if upper_bound < 2
    primes = [2]
    3.upto(upper_bound) do |n|
      is_prime = !!! primes.detect { |prime| mult_of?(n, prime) }
      primes << n if is_prime
    end
    return primes
  end

  def mult_of?(n, factor)
    n % factor == 0
  end

Line 5 could be simplified to is_prime = primes.none? { |prime| mult_of?(n, prime) }