对elisp中的格式功能感到困惑

Question

我希望输出像0 1,但下面的代码只打印nil.我使用type-of来测试(第一个十六进制),它是整数.%d应该有效,对吧？如果我使用消息,它可以在Emacs中使用.

(defun draw-board (board)
  (loop for x below 2
        for hex = (aref board x)
        do (format "%d " (first hex))))

(draw-board [(0 2) (1 2) (0 3) (0 2)])

Answer 1

1- emacs lisp格式不是Common Lisp格式.注意缺少的参数!

(format "%d" 42) == (cl:format NIL "~D" 42)

2-因此你的循环所做的唯一事情是:

 - to check that board is a vector with at least two slots. (aref
   signals an error if the index is out of bound).

 - to check that each of those two slots are lists (first signals an
   error when passed a non list).

 - to check that the first element of each each of those two slots
   are numbers. (format signals an error when you pass a non number
   for %d).

就这样.

你从未说过要打印任何东西.

要打印某些内容,必须将其放在缓冲区中,并使用ps-print-buffer:

(defun draw-board (board)
  (with-temp-buffer
    (loop for x below 2
          for hex = (aref board x)
          do (insert (format "%d " (first hex))))
    (ps-print-buffer)))