Recursive fibonacci with memoization

gistfile1.rb

def memoize(name)
  cache = {}
  (class << self; self; end).send(:define_method, name) do |*args|
    cache[args] = super(*args) unless cache.has_key?(args)
    cache[args]
  end
end

def fib(n)
  return n if n < 2
  fib(n-1) + fib(n-2)
end

memoize(:fib)
fib(100) # => 354224848179261915075