fizzbuzz.rb

class Num
  def initialize(v)
    @v = v
  end

  def combine(target)
    target
  end
end

class FizzBuzz
  attr_reader :v

  def initialize(v)
    @v = v
  end

  def combine(target)
    FizzBuzz.new(@v + target.v)
  end
end

def fizzbuzz(n)
  fizz = [n].select { |e| e % 3 == 0 }.map { FizzBuzz.new('Fizz') }
  buzz = [n].select { |e| e % 5 == 0 }.map { FizzBuzz.new('Buzz') }
  fizz.concat(buzz).inject Num.new(n) do |x, y|
    x.combine(y)
  end
end