fibonacci

"""
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.
"""


describe 'sum even-valued Fibonacci sequence terms below 4 million' do
	it 'should be 4613732' do
		fib = Fib.new
		fib.sum_even_sequence.should == 4613732
	end
end

class Fib	
	def sum_even_sequence
		result = [1, 2]
		sum = 2
		i=2
		
		while result.last < 4_000_000
			total = result[i-1] + result[i-2]
			result << total
			sum += total if total.even?
			i += 1
		end
		
		return sum
	end
end

Ruby...? I think that this works, too:

def fib first, second, total=0
return total if second > 4000000
second.even? ? fib(second, first + second, total + second) : fib(second, first + second, total)
end