fib.coffee

sys = require('sys')
crypto = require('crypto')

key = (values) ->
  sha1 = crypto.createHash('sha1')
  sha1.update values.join('-')
  sha1.digest('hex')

memoize = (f, memo = {} ) -> (args...) -> memo[k = key(args)] or memo[k] = f args...

fib = (n) -> if n < 2 then n else fib(n-1) + fib(n-2)
fib = memoize(fib)

sys.p fib 10
sys.p fib 55 # cannot calculate without memo