#!/usr/bin/ruby -w
# Tue Nov 17 00:06:30 EST 2009
# patternexon AT gmail
# Under GPL v3.0
class Integer
/*
Sift the Twos and sift the Threes,
The Sieve of Eratosthenes.
When the multiples sublime,
The numbers that remain are Prime.
*/
def primes_upto(limit)
  primes = Array.new
  putative = Array(2..limit)
  putative.each_index do |i|
    primes.push(putative[i])
    (i+1).upto(putative.size-1) do |j|
      putative[j] = nil if putative[j] % putative[i] == 0
    end
   putative.compact!
 end
return primes
end
def prime?
  if self == self.primes_upto(self).last
    return true
  else
    return false
  end
end
end
 
1.upto(100){ |i| puts "#{i} is #{i.prime?}" }