Project Euler Problem 2

gistfile1.rb

#! /usr/bin/env ruby

# goal is to print the sum of all even fibonacci numbers under 4 million

def fibonacci
  a, b = 1, 2
  while true
    yield a
    a, b = b, a + b
  end
end

def fibonacci_up_to_n(n)
  fibonacci.take_while {|i| i < n}
end

even_fibonacci_up_to_4mil = fibonacci_up_to_n(4000000).select {|num| num.even?}

puts even_fibonacci_up_to_4mil.reduce(:+)