prime?

gistfile1.txt

def self.prime?(num)
  return num > 1 if num <= 3
  return false if (divisible?(num,2) || divisible?(num,3))

  # loop while (6*k-1)**2 <= num, or
  # k <= (1+sqrt(num)/6)
  max_k = (Math.sqrt(num)+1)/6.0
  return false if (1..max_k).any? {|k| divisible?(num,6*k+1) || divisible?(num,6*k-1)}
end

@KevinWMatthews -- will you post your updates to this, here in the gist? I'm curious to see what you come up with :D

Oh! Just saw this.