irb(main):050:0* def fib_to(max, i = i, j = 0)
irb(main):051:1>   exit if i > max
irb(main):052:1>   print "#{i}, "
irb(main):053:1>   fib_to(max, i += j, j = i)
irb(main):054:1> end
=> nil
irb(main):055:0> fib_to(10)
NameError: undefined local variable or method `i' for main:Object
        from (irb):50:in `fib_to'
        from (irb):55
        from :0