Personal website

Practice implementation

(defun my-within-order-of-magnitude-p (x y &optional n b)
  "Return t if X is within N orders of base-B magnitudes of Y.

By default, check for 1 order of base-10 magnitude."
  (let ((n (or n 1))
        (b (or b 10)))
    (and (> (/ (float x) y) (expt b (- 0 n)))
         (< (/ (float x) y) (expt b (+ 0 n))))))

(and (my-within-order-of-magnitude-p 1.00 1.01)
     (my-within-order-of-magnitude-p 1000 1010))

(seq-map (lambda (number)
           (list number
                 (my-within-order-of-magnitude-p 1 number)))
         (number-sequence 1 15))

1	t
2	t
3	t
4	t
5	t
6	t
7	t
8	t
9	t
10	nil
11	nil
12	nil
13	nil
14	nil
15	nil