(do
    (defun fact (n) 
        (if (<= n 0) 1 
            (* n (fact (- n 1)))))
    (defun print-fact (n) (println n "! = " (fact n)))

    (defun stirlings (n)
        (if (<= n 0) 1
            (* (sqrt (* 2 3.14159 n))
               (pow (/ n 2.718281) n))))

    (print-fact 5)
    
    (println "Stirling's approx. for 5! = " (stirlings 5)))