Evaluate e^x HackerRank Common Lisp implementation

series-expansion.lisp

(read) ;; Throwing this away. Not needed

(defun read-list ()
"reading in list of number"
    (let ((n (read *standard-input* nil)))
         (if (null n)
             nil
             (cons n (read-list)))))
             
(defun factorial! (number)
	"O(n)? naive but works: returns the factorial of the number given"
	(loop for x from 1 upto number
		  for y = 1 then (* x y)
		  finally (return y)))

(defun series-expansion (number)
"Evaluates e^x taking the first ten terms from the series expansion method"
	(+ (reduce #'+ (loop for i from 1 upto 9 collect (/ (float (expt number i)) (factorial! i)))) 1))

(format t "~{~d~%~}" (map 'list #'series-expansion (read-list))) ;; print the results

Not efficient. will revisit later.