memoization using a hash. from rubies in the rough

gistfile1.rb

def fibonacci(nth, series = method(:fibonacci))
  if nth < 2
    nth
  else
    series[nth - 2] + series[nth - 1]
  end
end

# The easiest memoization in the world:
fibs = Hash.new { |series, nth| series[nth] = fibonacci(nth, series) }

p fibs[100]

# put diffrently:
     fibonacci = Hash.new { |numbers, index|
       numbers[index] = fibonacci[index - 2] + fibonacci[index - 1]
     }.update(0 => 0, 1 => 1)
     p fibonacci[300]
 #    222232244629420445529739893461909967206666939096499764990979600