project_euler_2.rb

#!/usr/bin/env ruby

#Each new term in the Fibonacci sequence is generated by adding the previous two terms. 
#By starting with 1 and 2, the first 10 terms will be:
# 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
#By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

def fibo limit=4000000
  fib=[0,1]
  loop do
    fib << fib[-1] + fib[-2]
    break if (fib[-1] + fib[-2]) > limit
  end
  fib.select{|x| x%2 == 0}.inject{|sum,x| sum + x }
end

puts fibo