LISP - 将列表写入文件

Question

我需要将一个数字列表写入一个文件，并在该行的末尾放置一个return。

我试过这段代码，但只对列表的第一个元素有效。

(defun write-segment (filename segment)
  (cond ((null segment)
         (with-open-file (out filename 
                              :direction :output 
                              :if-exists :append 
                              :if-does-not-exist :create)
           (format out "~%")))
        (T (with-open-file (out filename 
                                :direction :output 
                                :if-exists :append 
                                :if-does-not-exist :create)
             (format out "~D " (first segment))
             (write-segment filename (cdr segment))))))

有人可以帮我解决这个问题吗？

Answer 1

像这样将 % 附加到流中怎么样:

(with-open-file (str "filename.txt"
                     :direction :output
                     :if-exists :supersede
                     :if-does-not-exist :create)
  (format str "~A~%" '(1 2 3 4 5)))

在你的情况下，我会做一些事情，比如遍历列表并写入流，像这样的事情，小心额外的返回，如果你不想做，你也可以在打开文件之前添加一个控件如果列表为空，则执行任何操作。

(defun write-non-empty-list-to-a-file (file-name lst)
  "writes a non empty list to a file if the list is empty creates the file with a return"
  (with-open-file (str file-name
                     :direction :output
                     :if-exists :supersede
                     :if-does-not-exist :create)
    (dolist (e lst)
      (format str "~A~%" e))
    (format str "~%")));this if you want an extra return