Tail recursion of Scheme.

Ruby program for Fibonacci number.

def fib(n)
 if n < 2
   n
 else
   fib(n - 2) + fib(n - 1)
 end
end

Scheme program for Fibonacci number.

(define (fib n)
 (if (< n 2)
   n
   (+ (fib (- n 1)) (fib (- n 2)))))

Tail recursion version.

(define (fib n)
 (define (fib-iter n a b)
   (if (zero? n)
     a
     (fib-iter (- n 1) b (+ a b))))
 (fib-iter n 0 1))

Scheme has "tail recursion optimization".
Then Scheme is faster than Ruby with optimization.