Ruby script to calculate Xth prime number.

prime_number_2.rb

#! /usr/local/bin/ruby
# coding: utf-8
# --------------------------------------
#   Calculate Xth prime number
# --------------------------------------

class PrimeNumber2
  def exec(no)
    n, i = 2, 0
    loop do
      i += 1 if is_prime(n)
      break if i == no
      n += 1
    end
    puts "#{i}th PRIME NUMBER: #{n}."
  end

private

  def is_prime(n)
    res = (2..Math.sqrt(n)).any? { |i| n % i == 0 }
    return res || n == 1 ? false : true
  end
end

PrimeNumber2.new.exec(100000) if __FILE__ == $0