lisp - 如何在 LISP 中列出从 1800 开始的所有闰年？

Question

我有下面这段代码，它接受一个参数并以相反的顺序打印所有闰年列表。我怎样才能让它以 1800 作为默认输入并运行命令 (leap) 来列出 1800-2018 的所有闰年？

代码:

(defun leap (q)

    (if (< q 1800)
        (RETURN-FROM leap nil)
    )

    (leap (- q 1))

    (if (leapyear q)
        (push q mylist)
    )
    mylist
)


(reverse(leap 2018))

Answer 1

我不能完全理解你想做什么，但是:

(defun leapyearp (y)
  ;; is Y a leap year, as best we can tell?
  (= (nth-value 3 (decode-universal-time
                   (+ (encode-universal-time 0 0 0 28 2 y)
                      (* 60 60 24))))
     29))

(defun leapyears (&key (start 1800) (end (nth-value 5 (get-decoded-time))))
  ;; all the leap years in a range
  (loop for y from start to end
        if (leapyearp y) collect y))