Lisp

(defun fib (n)
  (loop repeat n
     for x = 0 then y and y = 1 then (+ x y)
     finally (return y)))

Why do people think Lisp is functional again?

>>1
I think the reason for Lisp being strongly associated with functional programming is do its use of S expressions, if M expressions had been implemented (more conventional separation of function name to its parameters) then the "code is data" thing would never have taken off and we would have seen Lisp as a more Haskell-like language