1 defmodule SumOfEvenFibonacci do
2 def fibonacci_stream() do
3 items_with_prev = Stream.iterate({0,1}, fn({prev, curr}) -> {curr, prev + curr} end)
4 Stream.map(items_with_prev, fn({_, curr}) -> curr end)
7 def fibonacci_to(limit) do
8 Stream.take_while(fibonacci_stream(), fn(n) -> n < limit end)
11 def filter_even(stream) do
12 Stream.filter(stream, fn(n) -> rem(n, 2) == 0 end)
15 def even_fibonacci_to(limit) do
16 filter_even(fibonacci_to(limit))
20 IO.inspect(Enum.sum(SumOfEvenFibonacci.even_fibonacci_to(4_000_000)))