Recursive cached fibonnacci

fibonnacci.rb

fib = Hash.new do |hash, n|
  puts "calculating fib #{n}"
  
  # base case
  if n == 0 || n == 1
    hash[n] = 1
  else
    # recursive case
    hash[n] = hash[n - 1] + hash[n - 2]
  end
end


> fib[3]
# calculating fib 3
# calculating fib 2
# calculating fib 1
# calculating fib 0
# => 3

fib[1]
# => 1

> fib[5]
# calculating fib 5
# calculating fib 4
# => 8