FizzBuzz with Qualified Constants

A FizzBuzz with no modulo operator. Instead, I nest three T modules and five F modules, mark the innermost one with a zero method, and look up T::T::...::T with n segments.

require 'active_support/core_ext'

module T
  module T
    module T
      def self.zero; end
    end
  end
end

module F
  module F
    module F
      module F
        module F
          def self.zero; end
        end
      end
    end
  end
end

def fizz_buzz (n)
  mod3 = Object.qualified_const_get((["T"]*n).join("::"))
  mod5 = Object.qualified_const_get((["F"]*n).join("::"))
  if mod3.respond_to?(:zero) && mod5.respond_to?(:zero)
    "FizzBuzz"
  elsif mod3.respond_to?(:zero)
    "Fizz"
  elsif mod5.respond_to?(:zero)
    "Buzz"
  else
    n
  end
end

(1..20).map(&method(:fizz_buzz))
#=> [1, 2, "Fizz", 4, "Buzz", "Fizz", 7, 8, "Fizz", "Buzz", 11, "Fizz", 13, 14, "FizzBuzz", 16, 17, "Fizz", 19, "Buzz"]

When a lookup goes past the innermost module, Ruby’s constant resolution falls back to the top-level T (or F), so the chain wraps around and the module reached only responds to zero when n is a multiple of 3 (or 5).

Gist: fizzbuzz_constants.rb