related educational stuff: here's three different ways to do lazy sequences (infinite seqs) in python: generators, closures, and classes. provides implementations of lazy-map and lazy-filter for each style. (the generator implementations are equivalent to those in itertools.) uses fib instead of fac. https://github.com/dustingetz/sandbox/blob/master/etc/lazy.p...

we can use these ideas to elegantly solve the second greplin challenge question: "find the smallest prime fibonacci, X, greater than 227,000; compute sum of prime divisors of X+1"

  pred = lambda x: x > 227000 and is_prime(x)
  X = take(lazy_filter(pred, fib_gen()), 1)[0]
  print sum(filter(is_prime, divisors(X+1)))

https://github.com/dustingetz/sandbox/blob/master/etc/grepli...