Naïve binary gap implementation in Ruby

binary_gap.rb

def binary_gap(n)
  n.is_a?(Integer) or raise(ArgumentError, 'Must be an Integer')
  bits = n.digits(2)
  longest = current = 0
  bits.each do |d|
    if d == 0
      current += 1
    else
      longest = current if (current > longest)
      current = 0
    end
  end
  longest
end