check each prime in primes.txt

checkprimes.rb

#!/opt/local/bin/ruby1.9 -w
# -*- coding: utf-8 -*-
# checkprimes.rb: check each prime in primes.txt

PRIMES_FILE = "primes.txt"

$primes = []
if File.exist?(PRIMES_FILE)
  File.foreach(PRIMES_FILE) do |line|
    $primes.push(line.to_i)
  end
end

def prime?(n)
  return true if n == 2
  return false if n.even?
  d = 3
  limit = Math::sqrt(n)
  while d <= limit
    return false if (n % d == 0)
    d += 2
  end
  true
end

$primes.each do |p|
  print "#{p} is not a prime number.\n" if ! prime?(p)
end