memoized fibonacci

fib.rb

class Fib
  def fib(i)
    memory.fetch(i) do
      val = if i <= 1
              [i,0].max
            else
              fib(i-1) + fib(i-2)
            end
      memory[i] = val
    end
  end

  private

  def memory
    @memory ||= {}
  end
end

puts Fib.new.fib(10)