1.30

gistfile1.lisp

(defun cube (x) (* x x x))

(defun sum-iter (term a next b)
  (defun iter (a result)
    (if (> a b)
        result
    (iter (funcall next a) (+ result (funcall term a)))))
  (iter a 0))

(defun simp-integral (f a b n)
  (let ((h (/ (- b a) n)))
    (defun add-dx (x) (+ x (* 2 h)))
    (defun simp-term (a)
      (+ (funcall f a)
         (* 4 (funcall f (+ a h)))
         (funcall f (+ a (* 2 h)))))
    (* (/ h 3.0)
       (sum-iter #'simp-term a #'add-dx (- b (* 2 h))))
    ))

(simp-integral #'cube 0 1 100)