add ruby

Makefile

@@ -14,3 +14,4 @@ test:
 	@ time -f "%C : %E seconds" ./prime.py 100000 > /dev/null
 	@ time -f "%C : %E seconds" ./prime.lua 100000 > /dev/null
 	@ time -f "%C : %E seconds" ./prime.php 100000 > /dev/null
+	@ time -f "%C : %E seconds" ./prime.rb 100000 > /dev/null

prime.rb

+#!/usr/bin/env ruby
+
+def isPrime(num)
+  num_sqr = Math.sqrt(num)
+
+  return false if num_sqr % 1 == 0
+
+  (2..num_sqr.to_i).each do |n|
+    return false if num % n == 0
+  end
+
+  return true
+end
+
+primes = []
+i = 2
+
+while primes.count < ARGV.first.to_i do
+  primes << i if isPrime(i)
+  i += 1
+end
+
+puts primes