Fibonacci sequence in Ruby (recursion)

Question

I\'m trying to implement the following function, but it keeps giving me the stack level too deep (SystemStackError) error.

Any ideas what the problem mi

Answer 1

yet another ;)

def fib(n)
  f = Math.sqrt(5)
  ((((1+f)/2)**n - ((1-f)/2)**n)/f).to_i
end

will be convenient to add some caching as well

def fibonacci
  @fibonacci ||= Hash.new {|h,k| h[k] = fib k }
end

so we'll be able to get it like

fibonacci[3]  #=> 2
fibonacci[10] #=> 55
fibonacci[40] #=> 102334155
fibonacci     #=> {3=>2, 10=>55, 40=>102334155}