funcbuzz.rb

mod3 = ->(i) { (i % 3).zero? }
mod5 = ->(i) { (i % 5).zero? }
both = ->(i) { mod3[i] && mod5[i] }

rules = {
  'FizzBuzz' => ->(i) { both[i] },
  'Fizz'     => ->(i) { mod3[i] },
  'Buzz'     => ->(i) { mod5[i] }
}

fizzbuzz = ->(i) {
  val, match = rules.detect { |val,rule| rule[i] }
  match ? val : i
}

puts (1..35).map &fizzbuzz

funcrubybuzz.rb

# Usage: FizzBuzz[100]
module FizzBuzz
  extend self

  MOD3 = ->(i) { (i % 3).zero? }
  MOD5 = ->(i) { (i % 5).zero? }
  BOTH = ->(i) { MOD3[i] && MOD5[i] }

  def [](count)
    (1..count).map &fizzbuzz
  end

  def fizzbuzz
    ->(i) {
      val, match = rules.detect { |val,rule| rule[i] }
      match ? val : i
    }
  end

  def rules
    {
      'Fizz'     => ->(i) { MOD3[i] },
      'Buzz'     => ->(i) { MOD5[i] },
      'FizzBuzz' => ->(i) { BOTH[i] }
    }
  end
end

puts FizzBuzz[35]